Question 1 :
An electricity bulb of 100 watt is connected to supply of electricity of 220V. Resistance of filament is
Question 2 :
An energy source will supply constant current into the load if its internal resistance is :
Question 7 :
The equivalent resistance due to series connection of $10 \Omega$ and $10 \Omega$ resistors is <br/>
Question 8 :
There are three resistance $5\Omega\, ,\, 6\Omega$ and $8\Omega$connected inparallel to a battery of 15 V and of negligible resistance. The potential drop across $6\Omega$ resistance is
Question 9 :
Two cells of emf's approximately $5$V and $10$V are to be accurately compared using a potentiometer of length $400$cm.
Question 10 :
Which among the following is the commercial unit of electric power?
Question 11 :
A resistor with the color coded value of 1000 ohms and 10% tolerance can have an actual resistance between<br>
Question 12 :
If the temperature of a conductor is increased, its resistance will<br><br>
Question 13 :
There are three resistance 5$\Omega$, 6$\Omega$ and 8$\Omega$connected inparallel to a battery of 15 V and of negligible resistance.The potential drop across 6$\Omega$resistance is
Question 14 :
A solid spherical non-conductor of radius<b> 5 cm</b> has the potential of <b>50 V</b> at its outer surface. The potential atits center is
Question 15 :
The length of a conductor is doubled and its radius is halved, its specific resistance is
Question 17 :
Rate at which electric work is done is called as ?<br/>
Question 18 :
In the 5 band color resistor,which color bands are considered as significant digits?
Question 19 :
If $\displaystyle { R }_{ 1 }$ and$\displaystyle { R }_{ 2 }$ are respectively the filament resistance of a 200 watt bulb and 100 watt bulb designed to operate on the same voltage then.
Question 20 :
Two resistors of 30and 20 are joined together inseries and then placed in parallel with a 50 resistor.What is the effective resistance of thecombination?
Question 21 :
In comparing e.m.f.s of 2 cells with the help of potentiometer, at the balance point, the current flowing through the wire is taken from:<br/>
Question 22 :
When n number identical cell of emf E and internal resistanceis connected in parallel, the net emf of the system will be <br>
Question 23 :
The potential gradient along the length of a uniform wire is $10$ volt/m B and C are two points at $30$ cm and $60$ cm in a scale fitted along the wire. The pd between B and C is<br>
Question 27 :
An electrical device operate at 12 A current and 120 V D.C . If it is connected with 250 V and 30 Hz AC. then power consumption:
Question 28 :
Which of the following is not true for wire wound resistor?
Question 29 :
In our houses all electrical devices operate on 220 V. It implies that
Question 30 :
Assertion(A) : The e.m.f of the cell in secondary circuit must be less than e.m.f of cell in primary circuit in potentiometer.<br/>Reason (R): Balancing length cannot be more than length of potentiometer wire.<br/>
Question 31 :
A cell of emf $E$ is connected across a resistance $R$ . The potential difference between the terminals of the cell is found to be $V$ . The internal resistance of the cell is given as :
Question 32 :
$\displaystyle P=\frac { { V }^{ 2 } }{ R }$ is applied when
Question 33 :
State whether given statement is True or False<br/>The sum of all the voltage drops around a single closed loop in a circuit is zero.
Question 35 :
If n resistance (each R) are connected in series then their resultant will be
Question 37 :
Calculate the power of a source if it produces an energy of 250 joules in 10 sec.
Question 38 :
Kirchhoff's law of junction, $\displaystyle \sum { I } =0$, is based on
Question 40 :
For a heater rated at $4 \  kW$; $220 \  V$ . Calculate the resistance of the heater element.
Question 43 :
The resistance of a wire at room temperature $30^o C$ is found to be $10 \Omega $. Now to increase the resistance by 10%, the temperature of the wire must be [The temperature coefficient of resistance of the material of the wire is $0.002 \,per\, ^oC$].
Question 44 :
In comparing e.m.f. of two cells with the help of a potentiometer, at the balance point, the current flowing through the wire is taken from
Question 45 :
The resistance of a semiconductor material(germanium or silicon) ________with risein temperature.
Question 47 :
The resistance of a semiconductor material (germanium or silicon)_______ with rise in temperature.
Question 49 :
Taking the resistivity of platinoid as $3.3 \times 10^{-7}  m$, find the resistance of $7.0 m$ of platinoid wire of average diameter $0.14 cm$. 
Question 51 :
Two electric bulbs whose resistance are in the ratio of $1 : 2$ are connected in parallel to a constant voltage source. The ratio of the power dissipated in them will be:
Question 52 :
Each of Kirchoff's two laws presumes that some quantity is conserved.Which row states Kirchhoff's first law and names the quantity that is conserved?<br>
Question 53 :
A potentiometer circuit has been set up for finding the internal resistance of a given cell. The main battery,used across the potentiometer wire, has an emf of 2.0 V and a negligible internal resistance. Thepotentiometer wire itself is 4 m long. When the resistance, R, connected acrose the given cell, has valuesof<br>(i) infinity (ii) $9.5\Omega$<br>The 'balancing lengths, on the potentiometer wire are found to be 3m and 2.85 m, respectively.The value of internal resistance of the cell is
Question 54 :
Write true or false for the following statements :<br>Electric power is also called BOTU.
Question 55 :
In a potentiometer wire experiment, the emf of a battery in the primary circuit is $20V$ and its internal resistance is $5\space\Omega$. There is a resistance box in series with the battery and the potentiometer wire, whose resistance can be varied from $120\space\Omega$ to $170\space\Omega$. Resistance of the potentiometer wire is $75\space\Omega$. The following potential differences can be measured using this potentiometer
Question 57 :
If the resistance of a conductor is 5 $\Omega$ at 50$^o$ C & 7$\Omega$ at 100$^o$C, then mean temperature coefficient of resistance (of material) is
Question 59 :
The electric power is supplied through the copper wires from a one city to another city which is 150 km apart. If the terminal voltage and average resistance of per kilometer are 8 volt and 0.5 $\Omega$ respectively then the power loss in a wire is :
Question 60 :
There is a fixed potential difference between the two ends of a potentiometer. Two cells are connected in series in such a way that in one arrangement they help each other where as in the second arrangement they oppose each other. The balance point for these two combinations is obtained at 120 cm and 60 cm length respectively. The ratio of the emf of the cell is:
Question 61 :
A circuit consists of a resistance R connected to n similar cells. If the current in the circuit is the same whether the cells are connected in series or in parallel then the internal resistance r of each cell is given by
Question 62 :
A $4 m$ long wire of resistance $8\Omega$ is connected in series with a batterry of e.m.f. $2V$ and a resistor of $7\Omega$. The internal resistance of the battey is $1\Omega$. What is the potential gradient along the wire?
Question 63 :
Ashokbhai goes to an electric shop to buy an electric bulb to obtain light in a small room of his home. Which of the following statement is scientifically correct
Question 64 :
A potentiometer is an accurate and versatile device to make electrical measurements of E.M.F. because the method involves:
Question 65 :
Two identical cells connected in series send $1.0 A$ current through a $5 \ \Omega$ resistor. When they are connected in parallel, they send $0.8 \ A$ current through the same resistor. What is the internal resistance of the cell?
Question 67 :
A current passes through a resistor. If K$_1$ and K$_2$ represent the average kinetic energy of the conduction electrons and the metal ions respectively then
Question 68 :
The resistance of a 240 V ,200 W electric bulbwhen hot is 10 times the resistance when cold.The resistance at room temperature and thetemperature coefficient of the filament are <br>(givenworking temperature of the filament is 2000$^{0}$C)<br>
Question 69 :
When a battery connected across a resistor of $16 \Omega$, the voltage across the resistor is $12 V$. When the same battery is connected across a resistor of $10 \Omega$, voltage across it is $11 V$. The internal resistance of the battery (in $ohm$) is:
Question 70 :
Ina potentiometer experiment two cells of e.m.f and $E$ are used in series and in conjunction and the balancing length is found to be $58\ cm$ of the wire. If the polarity of $E$ is revered then the balancing length becomes $29\ cm$. The ratio $\dfrac{E_1}{E_2}$ of the e.m.f of the two cell is
Question 71 :
The sequence of bands in carbon resistor are brown, black, brown and gold, the value of resistance is (in $\Omega$)
Question 74 :
In the experiment of half deflection method the resistance R should be
Question 75 :
In the equation $AB = C$, A is the current density, C is the electric field, then B is
Question 76 :
A potential difference $V$ is applied to a copper wire of length $l$ and thickness $d$. If $V$ is doubled, the drift velocity:
Question 77 :
The resistance of a wire of length 100 cm and 7 x 10$^{-3}$ cm radius is 6 ohm. Its specific resistance is<br/>
Question 78 :
A potential difference of $2 V$ exists across a potentiometer wire of $2 m$ length. When the potential difference across a $2\Omega $ resistance of a second circuit is measured by the potentiometer wire, it amounts to $5 mm$ balancing length. The current in the second circuit is <br/>
Question 79 :
n identical cells are joined in series with its two cells A and B in the loop with reversed polarities.<br/>EMF of each shell is E and internal resistance r. Potential difference across cell A or B is:<br/>
Question 80 :
A brass disc and a carbon disc of same radius are assembled alternatively to make a cylindrical conductor. The resistance of the cylinder is independent of the temperature. The ratio of thickness of the brass disc to that of the carbon disc is $\underline{\hspace{0.5in}}$ .$\alpha$ is temperature coefficient of resistance & Neglect linear expansion
Question 81 :
What is the minimum number of bulbs, each marked $60W, \ 40V,$ that can work safely when connected in series with a $240V$ mains supply?
Question 82 :
The terminal voltage is $\dfrac{E}{2}$ when a current of $ 2\:A$ is flowing through $2\:\Omega $ resistance, then theinternal resistance of cell is :-<br>
Question 83 :
Electric power is transmitted over long distances through conducting wires at high voltage because
Question 84 :
If a heater draws $5 A$ current from a $240 V$ supply, what is the potential on the neutral wire?<br/>
Question 85 :
Twelve cells, each having an e.m.f of  E volt are connected in series and are kept in a closed box. Some of these cells are wrongly connected with positive and negative terminals reversed. This 12 cell battery is connected in series with an ammeter, an external resistance R ohms and a two-cell battery (two cells of the same type used earlier, connected perfectly in series). The current in the circuit when the 12-cell battery and 2-cell battery aid each other is 3A and is 2A when they oppose each other. Then the number of cells in 12-cells battery that are connected wrongly is:<br/>
Question 86 :
The temperature coefficient of resistance of a wire is $0.00125$ per $^oC$. At $300$K, its resistance is $1\Omega$. This resistance of the wire will be $2\Omega$ at.
Question 87 :
The temperature dependence of resistances of Cu and undoped Si in the temperature range $300-400$K, is best described by.
Question 88 :
A current is flowing in a circuit consisting of a resistor and a battery.<br/>What happens to the power dissipated in the resistor when the resistance is quadrupled and the voltage remains constant?
Question 90 :
If a cell of constant electromotive force produces the same amount of heat during the same time in two independent resistance $R_1$ and $R_2$, when connected separately one after the other, across the cell, then the internal resistance of the cell is
Question 91 :
In an electric iron heat produced is same, whether it is connected across an A.C. source or across 50 constant voltage. R.M.S, value of the A.C. voltage applied is
Question 92 :
Copper and silicon is cooled from 300 K to 60 K, the specific resistance :-
Question 93 :
If n number is identical resistors of resistance R are connected in parallel combination, then the effective resistance of the combination is ______
Question 94 :
To get maximum current in a resistance of 3 ohms, one can use n rows of m cells (connected in series) connected in parallel. If the total number of cells is 24 and the internal resistance of a cell is 0.5 ohms then
Question 95 :
If a bulb of 60 W is  connected across a source of 220 V, the current drawn by it is:
Question 96 :
A battery of e.m.f. $2.2  V$ and internal resistance $1.2  \Omega$ is connected to a potentiometer wire of length $10  m$ and resistance $9.8  \Omega$. The potential drop per cm of length of the wire is<br/>
Question 97 :
Resistances of $2 \Omega$ and $3 \Omega$ are connected in series. If the P.D across the $2 \Omega$ resistor is 3 V, the P.D across $3 \Omega$ is :
Question 98 :
$10$ wires (same length, same area, same material) are connected in parallel and each has $1\Omega$ resistance, then the equivalent resistancewill be
Question 100 :
A 3$\Omega $ resistor and a 6$\Omega $ resistor are connectedin parallel and the combination is connected inseries to a battery of 5V and a 3$\Omega $ resistor. Thepotential difference across the 6$\Omega $ resistor<br>
Question 101 :
A dynamo develops $0.5 A$ at $6 V$, the power delivered is ______.
Question 102 :
There are a large number of cells available, each marked $(6\ V, 0.5\Omega)$ to be used to supply current to a device of resistance $0.75\Omega$, requiring $24A$ current. How should the cells be arranged, so that power is transmitted to the load using minimum number of cells?
Question 103 :
Three resistors are connected in parallel across a potential difference and a current $I$ passes through it, the resistance values are such that $R_1 < R_2 < R_3$, then the ratio of branch currents in the same order is:
Question 104 :
Two heater coils separately take $10$ minute and $5$ minute to boil certain amount of water. If both the coils are connected in series, the time taken will be
Question 105 :
An ionization chamber with parallel conducting plates as anode and cathode, has $5\times 10^{7}$electrons and the same number of singly charged positive ions per $cm^{3}$. The electrons are moving towards the anode with velocity $0.4\ m/s$. Thecurrent density from anode to cathode is $4\mu A/m^{2}$. The velocity of positive ions moving towards cathode is
Question 106 :
Two unknown resistances are connected in two gaps of a meter-bridge. The null point is obtained at $40\ cm$ from left end. A $30\Omega$ resistance is connected in series with the smaller of the two resistances, the null point shifts by $20\ cm$ to the right end. The value of smaller resistance in $\Omega$ is
Question 107 :
The Kirchhoff's first law $(\displaystyle\sum i=0)$ and second law $\left(\displaystyle \sum iR=\displaystyle\sum E\right)$, where the symbols have their usual meanings, are respectively based on
Question 108 :
If an alternate current main supply is given to be $220 \ V$. What would be the average electro motive force during a positive half cycle:
Question 109 :
A $2$ resistor is connected in series with $R$ resistor. This combination is connected across a cell. When the potential difference across $2$ resistor is balanced on potentiometer wire, null point is obtained at length of $300cm$. When the same procedure is repeated for $R$ resistor, null point is obtained at length $350cm$, value of $R$ is <br/>
Question 111 :
Two resistance at $0^{\circ}C$ with temperature coefficient of resistance $\alpha_{1}$ and $\alpha_{2}$ joined in series act as a single resistance in a circuit. The temperature coefficient of their single resistance will be
Question 112 :
A constant potential difference is applied between the ends of the wire. If the length of the wire is elongated $4$ times, then the drift velocity of electrons will be:<br/>
Question 113 :
Resistance of 0.2 M solution of an electrolyte is 50 $\Omega $. The specific conductance of the solution of 0.5 M solution of the same electrolyte is 1.4 S $ m^{-1} $ and resistance of the same solution of the electrolyte is 280 $\Omega $. The molar conductivity of 0.5 M solution of the electrolyte is ?<br/>
Question 114 :
A cell sends a current through a resistance $R$ for time $t$. Now the same cell sends current through another resistance $r$ for the same time. If same amount of heat is developed in both the resistance, then the internal resistance of cell is
Question 115 :
Had the voltmeter been an ideal one, what would have been its reading?
Question 116 :
A cell of emf $E$ is connected to a resistance ${R}_{1}$ for time $t$ and the amount of heat generated in it is $H$. If the resistance ${R}_{1}$ is replaced by another resistance ${R}_{2}$ and is connected to the cell for the same time $t$, the amount of heat generated in ${R}_{2}$ is $4H$. Then internal resistance of the cell is:
Question 117 :
An alternating voltage $V=30\ \sin {50t}+40\ \cos {50t}$ is applied to a resistor of resistance $10\ \Omega$. The rms value of current through resistor is:
Question 119 :
Two metallic wires $A$ and $B$ of equal dimensions but made of different materials, having resistivities $\rho$ and $2\rho$, temperature coefficients of resistivities $2\alpha$ and $\alpha$ are connected in series. The temperature coefficient of resistance of the composite wire equals:
Question 120 :
When a battery sends current through the resistances <span class="MathJax"><span class="math"><span class="mrow"><span class="msubsup"><span class="mi">$R<span class="mn">_1$ and $R_2<span class="MJX_Assistive_MathML">R$, the internal resistance of battery is :<br/>
Question 121 :
The resistivity of a potentiometer wire is $\rho$ and the area of cross section of the wire is $A$. If the current flowing in the circuit is $I$, then potential gradient will be
Question 122 :
You are given $5   m$ length of heating wire, it has resistance of $24   \Omega$. It is cut into two and connected to $110$ volt line individually. The total power for the two half lengths is:
Question 123 :
When terminals of a cell of emf 1.5 V are connected to ammeter of resistance $4\Omega$, the ammeter reads 0.30A. Which of the following statements are correct?<br>
Question 124 :
The equivalent resistance of eight equal resistances in series is $48$ ohms. What would be the equivalent resistance if they are connected in parallel?
Question 126 :
Two parallel straight conductors carrying currents 5A each repel other with a force of $25 \times 10^{-5} Nm^{-1}$. The distance between the conductors is
Question 128 :
The length of potentiometer wire is 10 m and is connected inseries with an accumulator. The e.m.f. of a cell balances against 250 cm length of wire. If the length of potentiometer wire is increased by 1m, calculate the new balancing length of wire.
Question 130 :
A circular loop has a resistance of $40 \Omega$. Two points P and Q of the loop, which are one-quarter of the circumference apart are connected to a 24 V battery, having an internal resistance of $0.5\Omega$. What is the current flowing through the battery?
Question 131 :
A current of $I$ ampere flows through a resistance $R$ when connected across a cell of emf $E$ and internal resistance $1 \Omega$. When $R$ is increased by $50\%$, the current through the circuit is $0.8 A$. The value of $R$ is :
Question 132 :
<br/>A cell of constant emf first connect to a resistance $R_1$ and then to connected to the resistance $R_2.$ If power delivered in both cases in the same then internal resistance of the cell
Question 133 :
In a potentiometer experiment, it is found that no current passes through the galvanometer when the terminals of the cell are connected across $52$cm of the potentiometer wire. If the cell is shunted by a resistance of $5\Omega$, a balance is found when the cell is connected across $40$cm of the wire. Find the internal resistance of the cell.
Question 134 :
The resistance of the series comb of two resistance is S. When they are joined in parallel the total resistance is P. If S=nP, then the minimum possible value of n is:
Question 135 :
If instantaneous current in a circuit is given by$l=(3+4sin\omega t)A$ os then the maximum value of current in the circuit is
Question 136 :
A current of $16 \ A$ is made to pass through a conductor in which the number density of free electrons is $\displaystyle 4\times { 10 }^{ 28 }{ m }^{ -3 }$ and its area of cross section is $\displaystyle { 10 }^{ -5 }{ m }^{ 2 }$. The average drift velocity of free electrons in the conductor is:
Question 137 :
A 50 V d.c power supply is used to charge a battery of eight lead accumulators, each of emf 2 V and internal resistance $1/8 \Omega$. The charging current also runs a motor connected in series with the battery. The resistance of the motor is $5 \Omega$ and the steady current supply is 4 A. The chemical power stored in the battery is
Question 139 :
In a Wheatstone bridge, three resistances P, Q and R are connected in the three arms and the fourth arm is formed by two resistances $S_1$ and $S_2$ connected in parallel. The condition for the bridge to be balanced will be
Question 141 :
The supply voltage to a room is 120 $V$. The resistance of the lead wires is 6 $\Omega$. A $60W , 120V$ bulb is already switched on. What is the decrease of voltage (in Volts )across the bulb, when a $240 W , 120 V $heater is switched on in parallel to the bulb?<br>
Question 142 :
The magnitude of electric field at different points along the length of the rod is given by
Question 143 : <p>A potentiometer wire has length $4$m and resistance $8\Omega$.What should be the resistance that must be connected in series with the wire and an accumulator of emf $2$V, so as to get a potential gradient $1$mV per cm on the wire?</p>
Question 144 :
In a potentiometer arrangement, a cell of emf 1.25 V gives a balance point at 35 cm length of the wire. Ifthe cell is replaced by another cell, the balance point shifts to 63 cm, then emf of the second cell is
Question 145 :
An Aluminium $\left ( \alpha =4\times 10^{-3}K^{-1} \right )$ resistance R$_{1}$ and a carbon $( \alpha =0.5\times 10^{-3}K^{-1})$ resistance R$_{2}$ are connected in series to have a resultant resistance of 36$\Omega $ at all temperatures. The values of R$_{1}$ and R$_{2}$ in $\Omega $ respectively are :<br/>
Question 146 :
Assertion: Ohm's law holds only for small currents in metallic wire not for high currents
Reason: For metallic wire resistance increases with decrease in temperature.
Question 147 :
The colour code of a carbon resistor is, Brown, Black, Brown and Red. The value of the resistor is?
Question 148 :
STATEMENT-1<br/>In a Meter Bridge experiment, null point for an unknown resistance is measured. Now, the unknown resistance is put inside an enclosure maintained at a higher temperature. The null point can be obtained at the same point as before by decreasing the value of the standard resistance.<br/><br/>STATEMENT-2<br/>Resistance of a metal increases with increase in temperature.<br/>
Question 149 :
The terminals of a $18 V$ battery with an internal resistance of $1.5 \Omega$ are connected to a circular wire of resistance $24 \Omega$ at two points distant at one quarter of the circumference of a circular wire. The current through the bigger arc of the circle will be
Question 150 :
Every atom makes one free electron in copper. If $1.1$ ampere current is flowing in the wire of copper having 1mm diameter, then the drift velocity (approx) will be (density of copper = $9 \times 10^3 kg/m^3$ and atomic weight of copper = $63$)<br>
Question 151 : <span class="wysiwyg-font-size-small"><span class="wysiwyg-font-size-small"><p class="wysiwyg-text-align-left">When air is replaced by a dielectric medium of constant $K$, the capacity of the condenser:</p>
Question 152 :
When a thin mica sheet is placed between the plates of a condenser then the amount of charge, so compared to its previous value, on its plates will become:
Question 153 :
Which material sheet should be placed between the plates of a parallel plate condenser in order to increase its capacitance ?
Question 154 :
When a dielectric is introduced between the plates of a condenser, the capacity of condenser :<br/>
Question 155 :
A sheet of aluminium foil of negligible thickness is introduced between the plates of a capacitor. The capacitance of the capacitor :<br/>
Question 157 :
A parallel plate capacitor is charged. If the plates are pulled apart
Question 158 :
The capacity of a parallel plate capacitor with no dielectric substance but with a separation of $0.4cm$ is $2\mu F$. If the separation is reduced to half and it is filled with a dielectric substance of value $2.8$, then the final capacity of the capacitor is
Question 159 :
A capacitor consists of two metal plates each$10{\text{ }}cm$ by$20{\text{ }}cm;$ they are separated by a$2.0{\text{ }}mm$ thick insulator with dielectric constant$4.1$ and dielectric strength 6.0107 V/m. What is the capacitance in$pF\left( {{{10}^{ - 12}}F} \right)?$<br>
Question 160 :
A parallel plate capacitor C is charged by connecting it to a battery using a switch S as shown in the figure, Now S is opened and the plate separation is then increased. As a result:
Question 161 :
Displacement current goes through the gap between the plates of a capacitor when the charge of the capacitor
Question 162 :
If on combining two charged bodies, the current does not flow then :<br/>
Question 163 :
A parallel plate capacitor is charged and then isolated. What is the effect of increasing the plate separation on charge, potential, capacitance, respectively?<br>
Question 164 : <span class="wysiwyg-font-size-small"><span class="wysiwyg-font-size-small"><p class="wysiwyg-text-align-left">In a parallel plate condenser if the distance between the plates is made half and the dielectric constant is doubled, then the capacity increases by a factor:</p>
Question 165 :
If the inductance and capacitance are both doubled in L-C-R circuit, the resonant frequency of the circuit will :
Question 167 : <span class="wysiwyg-font-size-small"><span class="wysiwyg-font-size-small"><p class="wysiwyg-text-align-left">The capacity of a parallel plate condenser consisting of two plates each of $10\ cm^2$, separated by a distance of $2\ mm$ is:</p><p class="wysiwyg-text-align-left">(Take air as the medium between the plates)</p>
Question 168 :
Two parallel plate air capacitors have the same separation. The plates of the first are squares of side 10 cm. The plates of the second are squares of side 20 cm. The ratio of their capacitance is :
Question 169 :
A capacitor of capacitance $2\ \mu F$ is charged to a voltage of $6\  V$. The charge on its plates is:
Question 170 : <span class="wysiwyg-font-size-small"><span class="wysiwyg-font-size-small"><p class="wysiwyg-text-align-left">Force acting upon a charged particle kept between the plates of a charged condenser is F.If one of the plates of the condenser is removed,force acting on the same particle will become</p>
Question 171 : <span class="wysiwyg-font-size-small"><span class="wysiwyg-font-size-small"><p class="wysiwyg-text-align-left">Select correct Statements : </p><p class="wysiwyg-text-align-left">a) Charge cannot be isolated</p><p class="wysiwyg-text-align-left">b) Repulsion is the sure test to know the presence of charge</p><p class="wysiwyg-text-align-left">c) Waxed paper is dielectric in paper capacitor</p><p class="wysiwyg-text-align-left">d) Variable capacitor is used in tuning circuits in radio</p>
Question 172 : <p class="wysiwyg-text-align-left"><span class="wysiwyg-font-size-small"><span class="wysiwyg-font-size-small">Three capacitors $2\mu F, 3\mu F$ and $5\mu F$ <span class="wysiwyg-font-size-small"><span class="wysiwyg-font-size-small">are connected in parallel. The capacitance of the combination:</p>
Question 173 : <p class="wysiwyg-text-align-left">There are $10$ condensers each of capacity $5\; \mu F$. The ratio of minimum to maximum capacity obtained from these condensers will be :<br/></p>
Question 174 : <p class="wysiwyg-text-align-left"><span class="wysiwyg-font-size-small"><span class="wysiwyg-font-size-small">To obtain $3 \mu F$<i><span class="wysiwyg-font-size-medium"><span class="wysiwyg-font-size-medium"> </i><span class="wysiwyg-font-size-small"><span class="wysiwyg-font-size-small">capacity from three capacitors of <span class="wysiwyg-font-size-medium"><span class="wysiwyg-font-size-medium"><span class="wysiwyg-font-size-small">$2 \mu F$<i><span class="wysiwyg-font-size-medium"><span class="wysiwyg-font-size-medium"> </i><span class="wysiwyg-font-size-small"><span class="wysiwyg-font-size-small">each, they will be arranged as follows:</p>
Question 175 :
From a supply of identical capacitors rated $8\ \mu F, 250\ V$, the minimum number of capacitors required to form a composite $16\ \mu F, 1000\ V$ capacitor is:
Question 176 :
Two capacitors of $1\mu F$ and $2\mu F$ are connected in series and this combination is changed upto a potential difference of $120$ volt. What will be the potential difference across $1 \mu F$ capacitor:
Question 177 :
Four capacitors of equal capacitance have an equivalent capacitance ${ C }_{ 1 }$ when connected in series and an equivalent capacitance ${ C }_{ 2 }$ when connected in parallel. The ratio $\dfrac { { C }_{ 1 } }{ { C }_{ 2 } } $ is
Question 178 :
For capacitors in the series combination, the total capacitance C is given by<br/><br/>
Question 179 :
Find the total capacitance for three capacitors of $10$f,$15$f and $35$f in parallel with each other?
Question 180 :
Two capacitors of capacity $C_1$ and $C_2$ are connected in parallel, then the equivalent capacity is:
Question 181 : <span class="wysiwyg-font-size-small"><span class="wysiwyg-font-size-small"><p class="wysiwyg-text-align-left">In a charged capacitor the energy is stored in<b>:</b></p><b><span class="wysiwyg-font-size-small"><span class="wysiwyg-font-size-small"></b>
Question 182 :
Two parallel-plate of capacitor have charges +Q and -Q and potential difference $\triangle V$ due to charging, Now the capacitor is disconnected then the potential difference and the stored electrical potential energy is:
Question 183 :
A potential difference of $\Delta V$exists between two plates of a parallel-plate capacitor with capacitance C . A dielectric with a dielectric constant of kis then placed between the plates of the capacitor. What is the energy stored in the capacitor?
Question 184 :
If the charge on the condenser of $10\mu F$ is doubled, then the energy stored in it becomes ____________.
Question 185 :
A capacitor having capacity of $2.0\mu F$ is charged to $200\ V$ and then the plates of the capacitors are connected to a resistance wire. The heat produced in joule will be :
Question 186 :
The capacity of a condenser is 20$\mu F$ $\displaystyle $ and the potential is 20 V. The energy released an discharging it fully will be
Question 187 :
A $2 \mu F$ capacitor is charged to $100 V$ and then its plates are connected by a conducting wire, the heat produced is :
Question 188 :
The energy stored in a capacitor of capacitance C having a charge Q under a potential $V$ is
Question 189 :
The amount of work done is increasing the voltage across the plates of a capacitor from $5V$ to $10V$ is $W$. The work done in increasing it from $10V$ to $15V$ will be :
Question 190 :
The potential energy of system of two equal negative point charges of $2\mu C$ each held 1 m apart in air is ($k = 9 \times 10^9\, SI \,unit$)
Question 191 :
The capacitance of a variable capacitor joined with the battery of $100$V is changed from $2\mu F$ to $10\mu F$. What is the change in the energy stored in it?
Question 192 :
The capacity of a condenser is $4 \times 10^{-6}$ farad and its potential is 100 volts. The energy released on discharging it fully will be
Question 193 :
The energy stored in a capacitor of capacitance $C$ having a charge $Q$ under a potential $V$ is
Question 194 :
A capacitor of capacity C$_{1}$ charged up to V volt and then connected to an uncharged capacitor C$_{2}$.Then final P.D. across each will be:
Question 195 :
$R=100\ k\Omega$ and $C=1\ \mu F$ are connected in a series with a $12\ volt$ battery. What is the maximum energy stored in the capacitor:
Question 196 :
A metallic sphere of radius $18cm$ has been given a charge of $5\times { 10 }^{ -6 }C$. The energy of the charged conductor is :
Question 197 :
A 16 pF capacitor is connected to 70 V supply. The amount of electric energy stored in the capacitor is:
Question 198 :
If a capacitor having capacitance of $1200\mu F$ is charged at a uniform rate of $100\mu C/s$, what is the time required to increase its potential by $20$ volts?
Question 199 :
A parallel plate capacitor of $1\mu F$ capacity is discharging through a resister. If its energy reduces to half in one second. The value of resistance will be?
Question 200 : <span class="wysiwyg-font-size-small"><span class="wysiwyg-font-size-small"><p class="wysiwyg-text-align-left">The energy stored in a sphere of $10$ cm radius when the sphere is charged to a potential difference of $300$ V is</p>
Question 201 :
An automobile spring extends 0.2 m for 5000N load. The ratio of potential energy stored in this spring when it has been compressed by 0.2 m to the potential energy stored in the $10\mu{F}$ capacitor at a potential difference of 10000V will be:
Question 202 :
A pendulum with a bob hanging is suspended such that the electric field is in upward direction. At equilibrium of the bob, the change in tension in the string will be (assuming rest condition) :<br/>
Question 203 :
A variable air capacitor has $11$ movable plates and $12$ stationary plates, The area of each plate is $0.0015\ m^{2}$ and separation between opposite plates is $0.001\ m$. The maximum capacitance of the capacitor is
Question 204 :
The relative permittivity of water is 81. If $\varepsilon_0$ and $\varepsilon$ are permittivities of vaccum and water respectively Then:
Question 205 :
The potential across a $25.0$ microfarad capacitor is $5.0 V$.What is the charge on the capacitor?
Question 208 : <span class="wysiwyg-font-size-small"><span class="wysiwyg-font-size-small"><p class="wysiwyg-text-align-left">A parallel plate capacitor with plates separated by air acquires 1 $\mu $C of charge when connected to a battery of 500V. The plates still connected to the battery are then immersed in benzene ($k=2.25$). Then a charge flows from the battery is :<br/><span class="wysiwyg-font-size-small"><span class="wysiwyg-font-size-small"></p>
Question 209 :
Charges of $\dfrac{10}{3} mC$ are placed at the four vertices of a square of side $8cm$. The electric potential at the centre is :
Question 210 :
In a regular polygon of n sides, each corner is at a distance r from the centre. Identical charges are placed at (n-1) corners. At the centre, the magnitude of intensity is E and the potential is V.The ratio V/E is
Question 211 :
If dielectric is inserted in charged capacitor (battery removed ), then quantity that remains constant is. <br>
Question 212 :
In order to increase the capacity of parallel plate condenser one should introduce between the plates, a sheet of
Question 213 :
Two capacitators having capacitances $\displaystyle { C }_{ 1 }$ and $\displaystyle { C }_{ 2 }$ are charged with $120\  V$ and $200\  V$ batteries respectively. When they are connected in parallel now, it is found that the potential on each one of them is zero. Then:
Question 214 :
In a parallel plate capacitor, the distance between the plates is d & potential difference across plates is V. Energy stored per unit volume between the plates of capacitor is :<br/>
Question 215 :
A voltmeter reads $4\ V$ when connected to a parallel plate capacitor with air as a dielectric. When a dielectric slab is introduced between plates for the same configuration, voltmeter reads $2\ V$. What is the dielectric constant of the material?
Question 216 :
The voltage can be increased, but electric breakdown will occur if the electric field inside the capacitor becomes too large. The capacity can be increased by 
Question 217 :
A parallel plate condenser with plate separation d is charged with the help of battery so that $V_0$ energy is stored in the system. The battery is now removed. a plate of dielectric constant k and thickness d is placed between the plates of condenser. The new energy of the system will be :<br/>
Question 218 : <p class="wysiwyg-text-align-left"><span class="wysiwyg-font-size-small"><span class="wysiwyg-font-size-small">A parallel plate capacitor, at a capacity $100\; \mu F$, is charged by a battery at $50 \;V$. The battery remains connected and if the plates of the capacitor are separated so that the distance between them is reduced to half of the original distance, <span class="wysiwyg-font-size-small">the additional energy given by the battery to the capacitor in $J$ is:</p>
Question 219 :
A fully charged capacitor has a capacitance C. It is discharged through a small coil of resistancewire embedded in a thermally insulated block of specific heat capacity s and mass m. If the temperature of the block is raised by $\Delta $T, the potential difference V across the capacitance is :<br>
Question 220 :
A capacitor is charged by using a battery which is then disconnected. A dielectric slab is introduced between the plates which results in :<br/>
Question 221 :
The potential difference between the two plates of a parallel plate capacitor is constant. When air between the plates is replaced by dielectric material, the electric field intensity :<br/>
Question 222 :
Where should $q_3$ be placed to make the 'potential energy of the system equal to zero ?
Question 223 :
The surface densities on the surfaces of two charged spherical conductors of radii ${R}_{1}$ and ${R}_{2}$ are equal. The ratio of electric intensities on their surfaces is:
Question 224 :
A capacitor of capacitance C is connected to battery of emf $V_0$. Without removing the battery, a dielectric of strength $\varepsilon _r$ is inserted between the parallel plates of the capacitor C, then the charge on the capacitor is :<br/>
Question 225 :
The force of attraction between the plates of a charged condenser is :<br/>
Question 226 :
Two capacitors when connected in series have a capacitance of $3\mu F$, and when connected in parallel have a capacitance of $16\mu F$. Their individual capacities are :<br/>
Question 227 :
A battery is used to charge a parallel plate capacitor till the potential difference between the plates becomes equal to the electromotive force of the battery. The ratio of the energy stored in the capacitor and the work done by the battery will be :<br/>
Question 228 :
Two fixed charges separated by a distance $d$ experience a force $F$. A dielectric medium of thickness $\dfrac{d}{4}$ and dielectric constant $4$ is introduced in the space between them. Find the new force between the charges.
Question 229 :
The relation connecting the energy <i>U </i>and distance <i>r </i>between dipole and induced dipole is :<br/>
Question 230 :
A parallel plate air condenser has capacity of $20\mu F$. If the distance between two plates is doubled, then new capacity will be ________.
Question 231 :
A plane electromagnetic wave in a non magnetic dielectric medium is given by $\bar{E} = \bar{E_0} ( 4 \times 10^{-7} \times - 50 t)$ with distance being in meter and time in seconds. The dielectric constant of the medium is:
Question 233 :
The energy density in a parallel plate capacitor is given as $2.1\times10^{-9}\ J/m^{3}$. The value of the electric field in the region between the plates is
Question 235 : <span class="wysiwyg-font-size-small"><span class="wysiwyg-font-size-small"><p>A neutral hydrogen molecule has two protons and two electrons. If one of the electrons is removed we get a hydrogen molecular ion $\left ( H_{2}^{+} \right )$ . In the ground state of $ H_{2}^{+} $ the two protons are separated by roughly $1.5$ <br> $\ A^o$ and the electrons is roughly $1$ $A^o$ from each proton. The potential energy of the system is :</p>
Question 236 : <span class="wysiwyg-font-size-small"><span class="wysiwyg-font-size-small"><p class="wysiwyg-text-align-left">A charge $q$ of mass $m$ is released with a velocity $1\times 10^{6}\ m/s$ from a large distance from a fixed positive charge $Q$. The closest distance of approach is:</p>
Question 238 :
Intensity of an electric field (E) depends on distance $r$. In case of dipole, it is related as :<br/>
Question 239 :
Work done in placing a charge of$\displaystyle 8\times { 10 }^{ -18 }C$ on a condenser of capacitor $\displaystyle 100$ microfarad.
Question 240 :
In a $AC$ circuit the potential difference across an inductance and resistance joining in series are respectively $16\ V$ and $20\ V$. The total potential difference across the circuit is:
Question 241 :
Three point charges $3nC, 6nC$ and $9nC$ are placed at the corners of an equilateral triangle of side $0.1\ m$. The potential energy of the system is :
Question 242 :
The capacity of a parallel plate air capacitor is $2\mu F$ and voltage between the plates is changing at the rate of 3 V/s. The displacement current in the capacitor is :
Question 243 : <p class="wysiwyg-text-align-left"><span class="wysiwyg-font-size-small"><span class="wysiwyg-font-size-small">Two electric charges of $9\mu C$<i><span class="wysiwyg-font-size-medium"><span class="wysiwyg-font-size-medium"> </i><span class="wysiwyg-font-size-small"><span class="wysiwyg-font-size-small">and $-3\mu C$ <span class="wysiwyg-font-size-small"><span class="wysiwyg-font-size-small">are placed $0.16m$ apart in air. There will be a point P at which electric potential is $zero$ on the line joining the two charges and in between them. <span class="wysiwyg-font-size-small"><span class="wysiwyg-font-size-small">The distance of P from $9\mu C$ <span class="wysiwyg-font-size-small"><span class="wysiwyg-font-size-small">charge is:</p>
Question 244 :
An electron of mass $M_e$, initially at rest, moves through a certain distance in a uniform electric field in time $t_1$. A proton of mass $M_p$ also intially at rest, takes time $t_2$ to move through an equal distance in this uniform electric field. Neglecting the effect of gravity, the ratio $t_2 / t_1$ is nearly equal to :
Question 245 : <p class="wysiwyg-text-align-left"><span class="wysiwyg-font-size-small"><span class="wysiwyg-font-size-small">A capacitor acquires a potential difference<span class="wysiwyg-font-size-small"><span class="wysiwyg-font-size-small"> of $200\;V$ when $10^{12}$ electrons are taken from one plate and placed on the other plate. Its capacitance is:</p>
Question 246 :
Two capacitors $C_1$ and $C_2$ are connected in series, assume that $C_1 < C_2$. The equivalent capacitance of this arrangement is $C$, where
Question 247 :
Capacitance of a capacitor made by a thin metal foil is $2\mu F$. If the foil is folded with paper of thickness 0.15 mm, dielectric constant of paper is 2.5 and width of paper is 400 mm, the length of foil will be
Question 249 :
The potential of a large liquid drop when eight liquid drops are combined is $20 V$. Then the potential of each single drop was :
Question 250 : <p class="wysiwyg-text-align-left"><span class="wysiwyg-font-size-small"><span class="wysiwyg-font-size-small">Two electric charges <span class="wysiwyg-font-size-small"><span class="wysiwyg-font-size-small">$12\ \mu C$<i><span class="wysiwyg-font-size-medium"><span class="wysiwyg-font-size-medium"> </i><span class="wysiwyg-font-size-small"><span class="wysiwyg-font-size-small">and <span class="wysiwyg-font-size-small"><span class="wysiwyg-font-size-small">$-6\ \mu C$<i><span class="wysiwyg-font-size-medium"><span class="wysiwyg-font-size-medium"> </i><span class="wysiwyg-font-size-small"><span class="wysiwyg-font-size-small">are placed $20\ cm$ apart in air. There will be a point P, at which electric potential is zero on the line joining these two charges and outside excluding the region between them. The distance of P from $-6\ \mu C$ charge is:</p>
Question 251 :
The following operation can be performed on a capacitor:<br>X connect the capacitor to a battery of emf E.<br>Y disconnect the battery.<br>Z reconnect the battery with the polarity reversed.<br>W insert a dielectric slab in the capacitor.
Question 252 :
Assertion: STATEMENT-1 : To put a dielectric plate in the inter space between two plates of a capacitor connected to a D.C. voltage external agency has to do negative work.
Reason: STATEMENT-2 : Putting the dielectric increases the capacitance.
Question 253 :
A parallel plat capacitor is made of two circular plates separated by a distance of $5 mm$ and with a dielectric of dielectric constant $2.2$ between them. When the electric field in the dielectric is $3 \times 10^4$V/m, the charge density of the positive plate will be close to:
Question 254 :
The plates of a parallel plate capacitor are charged upto $100 V$.A $2 mm$ thick insulator shunt is inserted between the plates . Then to maintain the same potential difference ,the distance between the same potential difference , the distance between the capacitor plates is increased by $ 1.6 mm$.The dielectric constant of the insulator is
Question 255 :
A parallel-plate capacitor of plate area $A$ and plate separation $d$ is charged to a potential difference and then the battery is disconnected. A slab of dielectric constant $K$ is then inserted between the plates of the capacitor so as to fill the whole space between the plates. Find the work done on the system the process of inserting the slab.
Question 256 :
A parallel-plate air capacitor of capacitance $245 pF$ has a charge of magnitude $0.148\mu C$ on each plate. The plates are $0.328 mm$ apart. What is the surface charge density on each plate?<br/>
Question 257 :
The displacement current flows in the dielectric of a capacitor when the potential difference across its plate<br/>
Question 258 :
If an electron enters into a space between the plates of a parallel plate capacitor at an angle $\alpha$ with the plates and leaves at an angle $\beta$ to the plates. The ratio of it's kinetic energy while entering the capacitor to that leaving will be :<br/>
Question 259 :
At the moment $t=0$, an electron leaves one plate of a parallel-plate condenser with a negligible velocity. An accelerating voltage varying as $V=at$, where $a$ is a constant is applied between the plates. The separation between the plates is $l$. The velocity of the electron at the moment it reaches the opposite plate will be :<br/>
Question 260 :
In 1909, Robert Millikan was the first to find the charge of an electron in his now-famous oil-drop experiment. In that experiment, tiny oil drops were sprayed into a uniform electric field between a horizontal pair of oppositely charged plates.The drops were observed with a magnifying eyepiece, and the electric field was adjusted so that the upward force on some negatively charged oil drops was just sufficient to balance the downward force of gravity. That is, when suspended, upward force qE just equaled mg. Millikan accurately measured the charges on many oil drops and found the values to be whole number multiples of $1.6  \times 10^{-19} C$ the charge of the electron. For this, he won the Nobel prize. If a drop of mass $1.08 \times 10^{-14} kg$ remains stationary in an electric field of $1.68 \times 10^5 NC^{-1}$, then the charge of this drop is :<br/>
Question 261 :
A parallel plate air capacitor has a initial capacitance $C$. If plate separation is slowly increased from ${d}_{1}$ to ${d}_{2}$, then mark the correct statement(s). (Take potential of the capacitor to be constant, i.e., throughout the process it remains connected to battery.)<br>
Question 262 :
A capacitor of capacitance ${C}_{0}$ is charged to a potential ${V}_{0}$ and then isolated. A small capacitor $C$ is then charged from ${C}_{0}$, discharged and charged again. This process is being repeated $n$ times. Due to this, the potential of the larger capacitor is decreased to $V$. The value of $C$ is :<br/>
Question 263 :
A parallel plate condenser with a dielectric of dielectric constant $K$ between the plates has a capacity $C$ and is charged to a potential $V$ volt. The dielectric slab is slowly removed from between the plates and then reinserted. The net work done by the system in this process is :<br>
Question 264 :
Two similar parallel plate capacitors each of capacity $C_o$ are connected in series, The combination is connected with a voltage source of $V_o$. Now separation between the plates of one capacitor is increased by a distance $d$ and the separation between the plates of another capacitor is decreased by the distance $d/2$ The distance between the plates of each capacitor was $d$ before the change in separation. Then, select the correct choice :<br/>
Question 265 :
A parallel plate capacitor is charged from a cell and then isolated from it. The separation between the plates is now increased :<br/>
Question 266 :
A parallel plate capacitor is charged and then the battery is disconnected, When the plates of the capacitor are brought closer, then<br>
Question 267 :
A parallel plate capacitor is charged and then disconnected from the charging battery. If the plates are now moved farther apart by pulling at them by means of insulating handles, then:
Question 268 :
The energy of a parallel plate capacitor when connected to a battery is $E$. With the battery still in connection, if the plates of the capacitor are separated so that the distance between them is twice the original distance, then electrostatic energy becomes :<br/>
Question 269 :
A fully charged capacitor has a capacitance $C$. It is discharged through a small coil of resistance wire, embedded in a block of specific heat $s$ and mass $m$ under thermally isolated conditions. If the temperature of the block is raised by $\displaystyle \Delta T$, the potential difference $V$ across the capacitor initially is:
Question 270 : <span class="wysiwyg-font-size-small"><span class="wysiwyg-font-size-small"><p class="wysiwyg-text-align-left">The plates of a parallel plate capacitor are charged to $200\ V$ and then, the charging battery is disconnected. Now, a dielectric slab of dielectric constant $5$ and thickness $4\ mm$ is inserted between the capacitor plates. To maintain the original capacity, the increase in the separation between the plates of the capacitor is:</p>
Question 271 :
In 1909, Robert Millikan was the first to find the charge of an electron in his now-famous oil-drop experiment. In that experiment, tiny oil drops were sprayed into a uniform electric field between a horizontal pair of oppositely charged plates.The drops were observed with a magnifying eyepiece, and the electric field was adjusted so that the upward force on some negatively charged oil drops was just sufficient to balance the downward force of gravity. That is, when suspended, upward force qE just equaled mg. Millikan accurately measured the charges on many oil drops and found the values to be whole number multiples of $1.6  \times 10^{-19} C$ the charge of the electron. For this, he won the Nobel prize. Extra electrons on this particular oil drop (given the presently known charge of the electron) are :<br/>
Question 272 : <span class="wysiwyg-font-size-small"><span class="wysiwyg-font-size-small"><p class="wysiwyg-text-align-left">A parallel plate capacitor with air between the plates has a capacitance of $10\mu F$. The area of the capacitor is divided into two equal halves and filled with two media having dielectric constants $K_{1}=2$ and $K_{2}=4$. The capacitance of the system will be:<br/></p>
Question 273 :
Assertion: If three capacitors of capacitance $C_1 < C_2 < C_3$ are connected in parallel then their equivalent capacitance $C_{parallel} > C_{series}$
Reason: $\dfrac {1}{C_{parallel}}=\dfrac {1}{C_1}+\dfrac {1}{C_2}+\dfrac {1}{C_3}$
Question 274 :
A series combination of $n_1$ capacitors, each of value $C_1$, is charged by a source of potential difference 4 V. When another parallel combination of $n_2$ capacitors, each of value $C_2$, is charged by a source of potential difference V, it has the same (total) energy stored in it, as the first combination has. The value of $C_2$, in terms of $C_1$, is then<br>
Question 275 :
A very thin metal sheet is inserted halfway between the parallel plates of an air-gap capacitor. The sheet is thin compared to the distance between the plates, and it does not touch either plate when fully inserted. The system had capacitance, $C$, before the plate is inserted.<br>What is the equivalent capacitance of the system after the sheet is fully inserted?
Question 276 :
A parallel plate condenser has two circular metal plates of radius 15 cm. It is being charged so that electric field in the gap between its plates rises steadily at the rate of $10^12V/ms.$ what is the displacement current?
Question 277 :
A capacitor is charged by a cell of emf $E$ and the charging battery is then removed. If an identical capacitor is now inserted in the circuit in parallel with the previous capacitor, the potential difference across the new capacitor is :<br/>
Question 278 :
Two capacitors connected in parallel having the capacities $C_1$ and $C_2$ are given $'q'$ charge, which is distributed among them. The ratio of the charge on $C_1$ and $C_2$ will be :
Question 279 :
Three capacitance of capacity $10 \mu F , 5 \mu F $ are connected in parallel. The total capacity will be :
Question 280 :
A parallel plate capacitor has $91$ plates, all are identical and arranged with same spacing between them. If the capacitance between adjacent plates is $3\ pF$. What will be the resultant capacitance?
Question 281 :
The work done in placing a charge of $8\times  10^{-18} C$ on a condenser of capacity $100\mu F$ is :<br/>
Question 282 :
A parallel plate capacitor is charged and then the battery is disconnected, When the plates of the capacitor are brought closer, then<br>
Question 283 :
A parallel plate capacitor is charged from a cell and then isolated from it. The separation between the plates is now increased :<br/>
Question 284 :
A parallel plate condenser with a dielectric of dielectric constant $K$ between the plates has a capacity $C$ and is charged to a potential $V$ volt. The dielectric slab is slowly removed from between the plates and then reinserted. The net work done by the system in this process is :<br>
Question 285 :
A parallel plate air capacitor has a initial capacitance $C$. If plate separation is slowly increased from ${d}_{1}$ to ${d}_{2}$, then mark the correct statement(s). (Take potential of the capacitor to be constant, i.e., throughout the process it remains connected to battery.)<br>
Question 286 :
A parallel plate capacitor is charged and then disconnected from the charging battery. If the plates are now moved farther apart by pulling at them by means of insulating handles, then:
Question 287 :
A fully charged capacitor has a capacitance $C$. It is discharged through a small coil of resistance wire, embedded in a block of specific heat $s$ and mass $m$ under thermally isolated conditions. If the temperature of the block is raised by $\displaystyle \Delta T$, the potential difference $V$ across the capacitor initially is:
Question 288 :
The energy of a parallel plate capacitor when connected to a battery is $E$. With the battery still in connection, if the plates of the capacitor are separated so that the distance between them is twice the original distance, then electrostatic energy becomes :<br/>
Question 289 :
A fully charged capacitor has a capacitance '$C$'. It is discharged through a small coil of resistance wire embedded in a thermally insulated block of specific heat capacity '$s$' and mass '$m$'. If the temperature of the block is raised $'\Delta T'$, the potential difference '$V$' across the capacitance is :<br/>
Question 290 :
A fully charged capacitors has a capacitance $'C'$. It is discharged through a small coil of resistance wire embedded in a thermally insulated block of specific heat capacity $s$ and mass $m$. If the temperature of the block is raised by $\Delta T$, the potential difference $V$ across the capacitor is :<br/>
Question 291 :
A parallel-plate vacuum capacitor with plate area $A$ and separation $x$ has charges $+Q$ and $-Q$ on its plates. The capacitor is disconnected from the source of charge, so the charge on each plate remains fixed. What is the total energy stored in the capacitor?<br/>
Question 292 :
A$\displaystyle 40\mu F$capacitor in a defibrillator is charged to $3000 V$.The energy stored in the capacitor is setthrough the patient during a pulse of duration $2ms$, The power delivered to the patient is :
Question 293 :
The energy required to charge a parallel plate condenser of plate separation d and plate area of cross-section A such that the uniform electric field between the plates is E, is :<br/>
Question 294 :
A parallel plate capacitor without any dielectric within its plates, has a capacitance C, and is connected to a battery of emf V. The battery is disconnected and the plates of the capacitor are pulled apart until the separation between the plates is doubled. What is the work done by the agent pulling the plates apart, in this process?
Question 295 :
Three capacitors of same capacitance are connected in parallel When they are connected to a cell of $2$ volt, total charge of $1.8 \mu C$ is accumulated on them. Now after discharging they are connected m series and then charged by the same cell The total charge stored in them will be:
Question 296 :
Two condensers of capacity $0.3 \mu F$ and $0.6 \mu F$ respectively are connected in series. The combination is connected across a potential of $6$ volts. The ratio of energies stored by the condensers will be:
Question 298 : <span class="wysiwyg-font-size-small"><span class="wysiwyg-font-size-small"><p class="wysiwyg-text-align-left">A parallel plate capacitor has area of each plate A, the separation between the plates is d. It is charged to a potential V and then disconnected from the battery. The amount of work done in filling the capacitor completely with a dielectric constant k is :<br/></p>
Question 301 :
Find out on which of following factors does strength of the force between charged particles depend.<br/>
Question 302 :
the number of electric field lines emerged out of 1 C charge is
Question 303 :
Ordinary rubber is an insulator. But the specialrubber tyres of aircrafts are made slightlyconducting. Why is this necessary?
Question 304 :
A particle A has charge +q and a particle B has charge +4q. each having the same m . allowed to fall from rest through the same electric potential difference. the ratio of the speed of A to that of B will e
Question 305 :
What happens when a charged balloon is placed near another balloon of the same charge?
Question 306 :
The field due to a charge at a distance $x$ from it is $E$. When the distance is doubled, the intensity of the field would be:
Question 307 :
Which of the following may be discontinuous across a charged conducting surface?
Question 308 :
An electron (of charge $-e$) revolves around a long wire with uniform charge density $\lambda$ in a circular path of radius $r$. Its kinetic energy is given by:
Question 309 :
An uncharged insulator can be charged by ______ with another suitable body.<br/><br/>
Question 313 :
A steady curent i is flowing through a conductorof uniform cross-section. Any segment of theconductor has<br>
Question 314 : <span class="wysiwyg-font-size-small"><span class="wysiwyg-font-size-small"><p class="wysiwyg-text-align-left">Fill in the blank.</p><p class="wysiwyg-text-align-left">$1$ Coulomb of charge contains_______number of electrons.</p>
Question 315 :
A point charge ${q_1} =  - 5.8\mu C$ is held stationary at the origin . A second point charge ${q_2} =  + 4.3\mu C$ moves from the point $(0.26m,0,0)$ to $(0.38m,0,0)$.How much work is done by the electric force on {q_2}.
Question 316 :
The mud houses are cooler in summer and warmer in winter. It happen due to the reason that.
Question 317 :
The electric flux over a sphere of radius $1 m$ is $\phi$. If radius of the sphere were doubled without changing the charge enclosed, electric flux would become
Question 318 :
Calculate the magnitude of the force between two electrons which are separated by a distance of $10^{-10}m$. If the magnitude of the charge is $10^{-19}C$ and Coulomb constant is $10^{10}N\;m^{2}/C^{2}$.
Question 320 :
State whether the following statements are True or False.<br/>If E=0, at all points of a closed surface, The electric flux through the surface is zero.
Question 321 :
Two metallic spheres, one hollow and the other solid, have same diameter. The hollow sphere will hold charge
Question 322 :
The specific charge of a proton is $9.6 \, \times \, 10^7 \, C \, kg^{-1}$ The specific charge of an alpha particle will be
Question 323 :
The sum total of the number of electrons in a system may change. The statement is :<br/>
Question 324 :
An electric line of force in the $xy-plane$ is given by equation $x^{2} + y^{2} = 1$. A particle with unit positive charge, initially at rest at the point $x = 1, y = 0$ in the $xy - plane$.
Question 325 :
In Coulomb's law, the constant of proportionality K has the units $Nm^2/C^2$ then the magnitude of K in air is :<br/>
Question 326 :
Three identical charges, each having a value $1.0 \times 10 ^ { - 3 } \mathrm { C }$are placed at the corners of an equilateral triangle of side 20 cm Find the potential at the center of the triangle
Question 327 :
Two point charges with charges  $3$ micro coulombs and $4$ micro coulombs are separated by $2$ cm.The value of the force between them?
Question 329 :
A gold leaf electroscope is given a positive charge so that its leaves diverge. How is the divergence of leaves affected, when a negatively charged rod is brought near its disc?
Question 330 :
State whether true or false :Gauss law is applicable only when there is a symmetric distribution of charge.
Question 332 :
Two conducting charged spheres $X$ and $Y$ having unequal charges are connected by the wire. Which of the following is true?
Question 333 :
An electric dipole placed with its axis in the direction of a uniform electric field experiences:
Question 334 :
In an external electric field, the field line of force represent:<br/>
Question 336 :
An instrument used in electrostatics to detect thepresence of electric charge on a body is called ..............
Question 337 :
The process of charging a conductor from a chargedbody without touching them together is calledinduction
Question 339 : <span class="wysiwyg-font-size-small"><span class="wysiwyg-font-size-small"><p class="wysiwyg-text-align-left">If $10$ million electrons are removed from a neutral body, then the charge on the body is :</p>
Question 340 :
Electric field due to a point charge $q$ at distance $r$ has magnitude :<br/>
Question 342 :
A neutral water molecules$\displaystyle \left( { H }_{ 2 }O \right)$ in its vapour state has an electric dipole moment of$\displaystyle 6\times { 10 }^{ -30 }Cm$. If the molecule is placed in an electric field of$\displaystyle 1.5\times { 10 }^{ 4 }{ NC }^{ -1 }$, the maximum torque that the field can exert on it is nearly:
Question 343 :
Charging by friction is accompanied by loss or gain of electrons. State which body loses electrons when an ebonite rod is rubbed with fur.
Question 345 : <span class="wysiwyg-font-size-small"><span class="wysiwyg-font-size-small"><p class="wysiwyg-text-align-left">A charge of $5 C$ is placed at the centre of a spherical gaussian surface of radius $5 cm$. The electric flux through the surface is $\dfrac{1}{\varepsilon _{0}}$ times of</p>
Question 347 :
State True or False :Human body is a good conductor of electricity.
Question 349 :
Two electric dipoles of dipole moment $2 \space cm$ and $4 \space cm$ respectively are kept inside a cube of side $'a' \space m$. Total electric flux linked with the cube is (in SI units)
Question 350 :
The charges from one body can be Transferred to another body but the total charge of a system ...........<br>
Question 352 :
A point charge $q$ is palced on vertex of right circular cone. the semi-vertical angle of cone
Question 353 :
In a region of space, the electric field is given by $\vec{E}=8\hat{i}+4\hat{j}+3\hat{k}$. The electric flux through a surface of area $100$ units in the xy plane is :
Question 354 :
Two bodies have equal charge $q$, where each is charged with two electrons. One electron is transferred from the first body to the second so that one body has one excess electrons and other has three excess electrons while maintaining the distance between the charges. Which of the following statements are correct?I.The amount of electrostatic charge has decreased<br/>II.The electrostatic force between the pith balls has decreased<br/>III.Both the electrostatic charge and force have decreased
Question 356 :
A point charge is brought in an electric field. The electricfield at a nearby point
Question 357 :
A solid metallic sphere has a change $+ 3Q$. Concentric with this sphere is a conducting spherical shell having charge $-Q$. The radius of the sphere is 'a' and that of the spherical shell is $b\ (b > a)$. What is the electric field at a distance $R \ (a < R < b)$ from the centre?
Question 358 :
The electric flux through the curve surface of a cone. Due to a charge $Q$ placed at its mouth,
Question 359 :
A charge of magnitude $\mathit{Q}$ is placed at the origin. A second identical charge is placed at the position $\mathit{x=d}$ along the x-axis. Other than infinitely far away, at what position on the x-axis will a positive test charge experience a zero net force?
Question 361 :
A polythene piece rubbed with wool is found to have a negative charge of $3.6\times 10^{-7}C.$ Calculate the number of electrons transferred from wool to polythene:
Question 362 :
If the dipole of moment $2.57\times {10}^{-17} C.m$ is placed into an electric field of magnitude $3.0\times {10}^{4}N/C$ such that the fields lines are aligned at ${30}^{o}$ with the line joining the dipole, what torque will act on the dipole?
Question 364 :
When a plastic comb rubbed on hair is brought near bits of paper, it attracts them because:
Question 365 :
The Gaussian surface for calculating the electric field due to a charge distribution is?
Question 366 :
An electric dipole of moment $\vec { p } $ is placed normal to the lines of force of electric intensity $\vec { E } $, then work done in deflecting it through an angle of ${180}^{o}$ is:
Question 367 :
An electron and a proton equal momenta, enter a uniform magnetic filed at right angles to the field lines. What will be the ratio of the radii of an vature of three trajectories.
Question 368 :
Two positive point charges $q$ are placed at  $(a,0)$ and $(-a,0)$. A third positive charge $q_o$ is placed at $(0,y)$. For what value of $y$, the force on $q_o$ is maximum?
Question 369 :
Rub a piece of ebonite across a piece of animal fur. What happens?
Question 370 :
An electron beam accelerated from rest through a potential difference of $500V$ in vacuum is allowed to impinge on a surface normally. The incident current is $50\mu A$ and if the electrons come to rest on striking the surface the force on it is
Question 372 :
The electric flux over the surface of a sphere if it is charged with $10 \mu C$ is
Question 373 :
A cylinder of length $l$ and radius $R$ is placed in a uniform electric field $E$ parallel to the cylindrical axis. The total flux through the surface of the cylinder is given by
Question 374 :
If two charges of 1 coulomb are placed 1 km apart, the force between them will be:
Question 375 :
If two point charges of 1 coulomb each are placed 1 km apart in vaccum, the force between them will be:
Question 376 :
A surface encloses and electric dipole. The net flux through the surface is
Question 377 : <span class="wysiwyg-font-size-small"><span class="wysiwyg-font-size-small"><p class="wysiwyg-text-align-left">If the force between two charged objects is to be left unchanged even though the charge on one of the object is halved keeping the other same, the original distance (d) of separation should be changed to :<br/></p>
Question 378 : <p class="wysiwyg-text-align-left"><span class="wysiwyg-font-size-small"><span class="wysiwyg-font-size-small">A charge of $10^{-10}C$ <span class="wysiwyg-font-size-small"><span class="wysiwyg-font-size-small">is palced at the origin. The eletric field(in N/C) at $(1,1)$ cm due to it, is:</p>
Question 379 :
A charge of magnitude $Q$ is placed at the origin. A second charge of magnitude $2Q$ is placed at the position $x=d$ along the x-axis.<br>Other than infinitely far away, at what position on the x-axis will a positive test charge experience a zero net force?
Question 380 :
If both the spheres are connected by a conducting wire, then
Question 381 :
Assertion(A): Force between two point charges at rest is not changed by the presence of a third point charge between them.<br/>Reason (R): Force between two charges depends on the magnitude of the two charges and separation between them. then,
Question 382 :
An electric dipole is placed in an electric field generated by a point charge. Then
Question 383 :
The force acting between two opposite charges of equal magnitude is F. If $25\%$ charges are transferred from one to another, the force acting between them will be____.
Question 385 :
Why is electrical wiring usually made from copper and not silver?
Question 386 :
The force of interaction between any two point charges is proportional to :<br/>
Question 387 :
A certain charge Q is divided into two parts q and $Q-q$. How the charge Q and q must be related so that when q and $(Q-q)$ is placed at a certain distance apart experience maximum electrostatic repulsion?
Question 388 :
Assertion: Work done by the electrostatic field on a charge moving around a closed circular or elliptical path will be zero.
Reason: Electrostatic field is a conservative field.
Question 389 :
Two identical charged spheres suspended from a common distance $d(d < < 1)$ apart because of their mutual repulsion. The charged begin to leak from both the spheres at a constant rate. As a result, the spheres approach each other with a velocity $v$. Then $v$ varies as a function of the distance $x$ between the spheres, as
Question 390 :
A charged spherical conductor has a surface charge density of $0.07$ $C/m^{2}$ . When its charge is increased by $0.44C$, the charge density changes by $0.14$ $C/m^{2}$. The radius of the sphere is :<br>
Question 391 :
The force between two charges in different media are different because.
Question 393 :
Two particles $X$ and $Y$, of equal mass and with unequal positive charges, are free to move and are initially far away from each other. With $Y$ at rest, $X$ begins to move towards it with initial velocity $u$. After a long time, finally<br>
Question 394 :
An electron at rest has a charge of $1.6\ \times 10^{-19}\ C$. It starts moving with a velocity $v=c/2$, where $c$ is the speed of light, then the value the new charge on it is-
Question 395 :
Electric field due to an infinite sheet of charge having surface density $\sigma$ is $E$. Electric field due to an infinite conducting sheet of same surface density of charge is
Question 396 :
Assertion: STATEMENT-1 : The current density $\vec{J}$ at any point in ohmic resistor is in direction of electric field $\vec{E}$ at that point.
Reason: STATEMENT-2 : A point charge when released from rest in a region having only electrostatic field always moves along electric lines of force.
Question 397 :
A charge of $-30 \mu C$ is placed at 50 cm from another charge of $+25\mu C$ is vacuum. The force between them is:
Question 398 :
Assertion: Electrons in the atom are held due to coulomb forces.
Reason: The atom is stable only because the centripetal force due to Coulomb's law is balanced by the centrifugal force.
Question 399 :
What is the nature of Gaussian surface involved in Gauss law of electrostatic?
Question 400 :
The magnetic moment of a bar magnet of length $20\ cm$ is $3.6 \times 10^{-6} Am^{2}$. The magnetic length is $90\%$ of its geometric length. The pole strength is:
Question 401 : <span class="wysiwyg-font-size-medium"><span class="wysiwyg-font-size-medium"><p>A line joining places of zero dip is called</p>
Question 402 :
At the magnetic north pole of the earth, the value of the horizontal component of earth's magnetic field and angle of dip are respectively.
Question 404 :
The magnitude of the induced current in a closed coil increases with the increase in the strength of a magnet. The statement is<br/>
Question 405 :
Assertion: Magnetic susceptibility is a pure number.
Reason: The value of magnetic susceptibility for vacuum is one.
Question 407 :
The magnetic induction field strength at a distance 0.2 m on the axial line of a short barmagnet of moment 3.6 Am$^{2}$is
Question 409 :
Angle of dip at a place is $30^0 $. If the vertical component of earth's magnetic field at that point is $7.5\times 10^{-5}T$. then the total magnetic field of earth at that point will be :
Question 411 : <span class="wysiwyg-font-size-medium"><span class="wysiwyg-font-size-medium"><p class="wysiwyg-text-align-left">If horizontal and vertical components of the earth's magnetic field are equal at a certain place, then the angle of the dip at that place will be</p>
Question 412 :
A long solenoid has 1000 turns per meter and carries a current of 1 A. It has a soft Iron core of$ u_{r}= 1000 $. The core is heated beyond the Curie temperature,$ T_{e^{-}} $
Question 413 : <span class="wysiwyg-font-size-medium"><span class="wysiwyg-font-size-medium"><p>The direction of magnetic moment for a bar magnet is:</p>
Question 414 :
The relative permeability of a substance X is slightly less than unity and that of substance Y is slightly more than unity, then :<br/>
Question 415 :
The plane of a dip circle is set in the geographic meridian and the apparent dip is $\delta_1$. It is then set in a vertical plane perpendicular to the geographic meridian. The apparent dip angle is $\delta_2$. Then declination $\theta$ at the place is
Question 417 : <span class="wysiwyg-font-size-medium"><span class="wysiwyg-font-size-medium"><p class="wysiwyg-text-align-left">In the hystersis cycle, the value of H needed to make the intensity of magnetisation zero is called</p>
Question 419 :
Which of the following are best suited to make the core of a transformer?
Question 420 :
At $45^o$ to the magnetic meridian , apparent dip is $30^o$. Find true dip :<br/>
Question 422 :
A magnetic needle oscillates in a horizontal plane with a period T at a place where the angle of dip is $60^{0}$. When the same needle is made to oscillate in a vertical plane coinciding with the magnetic meridian, its period will be
Question 423 :
Materials suitable for permanent magnet, must have which of the following properties?
Question 427 :
The horizontal and vertical components of magnetic field of earth are same at some place on the surface of Earth. The magnetic dip angle at this place will be __________.
Question 429 :
The core of electromagnet is made of soft iron, because <br>a) susceptibility of soft iron is very high<br>b) coercivity of soft iron is very low
Question 430 :
A bar magnet has coercivity $4\times10^3 Am^{-1}$. It is placed in a solenoid having $40$ turns per cm and is $1.2m$ long. The current carried by the solenoid to demagnetize  the bar magnet is : <br/>
Question 431 :
A dip needle on a plane perpendicular to magnetic meridians will remain
Question 432 :
Assertion: There are two neutral points on a horizontal board when a magnet is held vertically on the board
Reason: At the neutral point the net magnetic field due to the magnetic and magnetic field of the earth is zero
Question 439 :
A bar magnet is cut into two equal haves by a plane parallel to the magnetic axis. Of the following physical quantities the one which remains unchanged is
Question 441 : <span class="wysiwyg-font-size-medium"><span class="wysiwyg-font-size-medium"><p class="wysiwyg-text-align-left">An iron specimen has relative permeability of 600 when placed in uniform magnetic field of intensity 110 amp. /m. Then the magnetic flux density inside is....... tesla.</p>
Question 443 :
The magnetic field of Earth can be modelled by that of a point placed at the center of the Earth. The dipole axis makes an angle of$ 11.3^{\circ} $ with the axis of Earth. At mumbai, declination is nearly zero. Then,
Question 445 :
Susceptibility of a magnetic substance is found to depend on temperature and the strength of the magnetising field. The material is a         <br/>
Question 446 :
Where are the field lines most concentrated around a bar magnet?
Question 448 : <span class="wysiwyg-font-size-medium"><span class="wysiwyg-font-size-medium"><p class="wysiwyg-text-align-left">A dip needle shows an angle of dip $\theta$ in a place which is in the magnetic meridian. Now, the dip circle is rotated through an angle $x$ in the horizontal plane and then it shows an angle of dip $\theta_{1}.$ Value of $\tan\theta_{1}/\tan{\theta}$ is :<br/></p>
Question 449 :
The length of a vertical pole at the surface of a lake of water $ \left(\mu=\frac{4}{3}\right)  $ is 24 $  \mathrm{cm} .  $ Then to an under-water fish just below the water surface the tip of the pole<br/>appears to be<br/>
Question 451 :
Assertion : Substances which at room temperature retain their ferromagnetic property for a long period of time are called permanent magnets.<br>Reason : Permanent magnet can be made by placing a ferromagnetic rod in a solenoid and passing current through it.
Question 452 :
Match the following and select the correct alternatives given below<br>(p) unit of magnetic induction B (q) dimensions of B<br>(r) unit of permeability $({\mu}_{o})$ (s) dimensions of${\mu}_{o}$<br>(t) dimensions of magnetic moment (u) $[ML{T}^{-2}{A}^{-2}]$<br>(v)$[M{L}^{0}{T}^{-2}{A}^{-2}]$ (x) Newton/amp-metre<br>(y) $Newton/{amp}^{2}$ (z) $[{M}^{0}{L}^{2}{T}^{0}A]$
Question 453 :
The total intensity of the earth's magnetic field at equator is $5$ units. What is its value at the poles?
Question 454 :
At a certain place the angle of dip is $ 30^0 $ and the horizontalcomponent of earth's magnetic field is 0.50 Oersted. The earth'stotal magnetic field is<br>
Question 455 :
A magnet makes 40 oscillations per minute at a place having magnetic fieldintensity of 0.1 X $10^{-5}$ T. At another place, it takes 2.5 seconds to complete one vibration. The value of earth's horizontal field at that place is
Question 456 :
The magnetic susceptibility of a paramagnetic substance is $3 \times 10^{-4} Am^{-1}$. The intensity of magnetisation will be : ( $H = 4 \times 10^3$ )
Question 458 :
At two places A and B using vibration magnetometer, a magnetvibrates in a horizontal plane and its respective periodic time are 2sec and 3 sec and at these places the earth's horizontal componentsare HA<br>and HB respectively. Then the ratio between HA and HB will be
Question 459 :
Assume the dipole model for earth's magnetic field B which is given by thevertical component of magnetic field, $B_V=\dfrac{\mu_o}{4\pi}\dfrac{2m\cos\theta}{r^3}$ and the horizontal component of magnetic field $B_H=\dfrac{\mu_o}{4\pi}\dfrac{m\sin \theta}{r^3}$, where $\theta =90^o-$latitude as measured from magnetic equator, then the loci of point for which dip angle is $\pm 45^o$.
Question 460 :
At a place, the horizontal and vertical components of earth's magnetic field are equal. What is the angle of dip at that place?
Question 461 :
A dip needle shows angle of dip $tan^{-1}\left( \frac{2}{\sqrt3}\right) $ in a vertical plane which is at an angle of $60^0$ with the magnetic meridian. The real dip at the place is then<br/>
Question 462 :
A coil of wire is placed in a changing magnetic field. If the number of turns in the coil is decreased, the voltage induced across the coil will
Question 465 :
The coercivity of a small magnet where the ferromagnet gets demagnetized is $3\times 10^{3}\ Am^{-1}$. The current required to be passed in a solenoid of length $10\ cm$ and number of turns $100$, so that the magnet gets demagnetized when inside the solenoid, is:
Question 466 :
At a given place on the earth's surface, the horizontal component of earth's magnetic field is $3 \times 10^{-6} T$ and resultant magnetic field is $6\times 10^{-6} T$. Angle of dip at this place is :<br/>
Question 468 :
The magnetic susceptibility of a paramagnetic material is $1.0\times { 10 }^{ -5 }$ at ${ 27 }^{ o }C$ temperature. Then, at what temperature its magnetic susceptibility would be $1.5\times { 10 }^{ -5 }$?
Question 469 :
Assertion: Magnetic moment of helium atom is zero.
Reason: All the electron are paired in helium atom orbitals
Question 470 :
If the magnetizing field on a ferromagnetic material is increased, its permeability
Question 471 :
A magnet falls with its S-pole along the axis of a ring. The current generated is ................ and acceleration is .................
Question 472 :
Assertion: Soft iron is used as transformer core.
Reason: Soft iron has narrow hysteresis loop
Question 473 :
Lines which represent places of constant angle of dip are called
Question 474 :
The intensity of magnetization of a bar magnet is $50 \times 10^4 Am^{-1}$. The magnetic length and the area of cross section of the magnet are 12 cm and 1 $cm^2$ respectively The magnitude of magnetic moment of this bar magnet is (in SI unit)
Question 477 :
Which of the following independent quantities is not used to specify the earth's magnetic field. ?
Question 478 :
When a ferromagnetic material is heated to temperature above itsCurie temperature, the material
Question 479 :
A magnet of dipole moment $2A{ m }^{ 2 }$ is deflected through ${30}^{o}$ from magnetic meridian. The required deflecting torque is $({ B }_{ H }=0.4\times { 10 }^{ -4 }T)$:
Question 481 :
Two coils P and Q are lying a little distance apart coaxially. If a current I is suddenly set up anti-clockwise in the coil P then the direction of current induced in coil Q will be : 
Question 482 :
A solenoid has a core of a substance with relative permeability $600$. What is the magnetic permeability of the given substance?
Question 483 :
An electron in a circular orbit of radius  $0.5A^{o}$ makes $7\times 10^{15}$ revolutions in each second. This electron orbit is equivalent to a magnetic shell of moment (in Am):<br/>
Question 484 :
Assertion: Magnetic field strength at a point on axial line of a bar magnet is along south to north pole of magnet.
Reason: The magnetic field strength can never be along north to south pole of a magnet.
Question 485 :
An electron revolving in an orbit of radius $0.5\mathring{A}$ in a hydrogen atom executes $10^{16}$ revolutions per second. The magnetic moment of electron due to its orbital motion will be
Question 486 :
Assertion: A current continues to flow in superconducting coil even after switch is off.
Reason: Superconducting coils show Meissner effect.
Question 487 :
Which of the following does earth's magnetic field deflect coming from outersphere?
Question 488 :
A magnetising force of $360 Am^{-1}$ produces a magnetic flux density of $0.6 T$ in a ferromagnetic material. The susceptibility of the material is:
Question 490 :
At a certain place, the horizontal component $ B_0 $ and the vertical component $ V_0 $ of the earth's magnetic field are equal in magnitude. the total intensity at the place will be
Question 491 :
If a magnet is suspended at angle ${30}^{o}$ to the magnetic meridian, the dip needle makes an angle of ${45}^{o}$ with the horizontal. The real dip is :
Question 492 :
At a temperature of ${30}^{o}C$, the susceptibility of a ferromagnetic material is found to be $\chi $. its susceptibility at ${333}^{o}C$ is
Question 493 :
A metallic circular ring is suspended by a string and is kept in a vertical plane. When a magnet is approached towards the ring, then it will :<br/>
Question 494 :
Which of the following is represented by the area enclosed by a hysteresis loop (B-H curve) ?
Question 495 :
A Conductor of length $l$ and mass $m$ can slide without any friction along two vertical conductors connected at the top through a capacitor. A uniform magnetic field B is set up perpendicular to the plane of the paper. The acceleration of the conductor 
Question 496 :
Magnetic induction on the axial line due to a short bar magnet is _____________ .<br/>
Question 497 :
Magnetic susceptibility $\chi$ of a paramagnetic material changes with absolute temperature $T$ as  
Question 498 :
The minimum magnetic dipole moment of electron in hydrogen atom is <br>
Question 499 : <span class="wysiwyg-font-size-medium"><span class="wysiwyg-font-size-medium"><p class="wysiwyg-text-align-left">The magnetic susceptibility of a magnetic<span class="wysiwyg-font-size-medium"><span class="wysiwyg-font-size-medium">material is $3\times 10^{-4}$<span class="wysiwyg-font-size-xx-small"><span class="wysiwyg-font-size-xx-small"> <span class="wysiwyg-font-size-medium"><span class="wysiwyg-font-size-medium">. Its relative permeability willbe</p>
Question 500 :
The resultant magnetic field at the center of a bar magnet is zero.<br>
Question 501 :
A domain in ferromagnetic iron is in the form of a cube of side length $2$ $\mu m$ then the number of iron atoms in the domain are (Molecular mass of iron $=55$g $mol^{-1}$ and density $=7.92$g $cm^{-3}$)
Question 502 :
 A direct current $I$ flows in a long round uniform cylindrical wire made of paramagnetic material with susceptibility $\chi$. Find the surface molecular current $I_s^\prime$.
Question 503 :
If $M_2$ = magnetization of a paramagnetic sample, B = external magnetic field, T = absolute temperature, C = curie constant then according to Curie's law in magnetism, the correct relation is
Question 505 :
The magnetic field at a point $x$ on the axis of a small bar magnet is equal to the field at a point $y$ on the equator of the same magnet. The ratio of the distance of $x$ and $y$ from the centre of the magnet is?
Question 506 : <p class="wysiwyg-text-align-left"><span class="wysiwyg-font-size-medium"><span class="wysiwyg-font-size-medium">A bar magnet of magnetic moment $M$<i><span class="wysiwyg-font-size-large"><span class="wysiwyg-font-size-large"> </i><span class="wysiwyg-font-size-medium"><span class="wysiwyg-font-size-medium">is divided <span class="wysiwyg-font-size-medium"><span class="wysiwyg-font-size-medium">into '$n$'<span class="wysiwyg-font-size-large"><span class="wysiwyg-font-size-large"> <span class="wysiwyg-font-size-medium"><span class="wysiwyg-font-size-medium">equal parts by cutting parallel to length. Then one part is suspended in a uniform magnetic <span class="wysiwyg-font-size-medium"><span class="wysiwyg-font-size-medium">field of strength $2T$<i><span class="wysiwyg-font-size-large"><span class="wysiwyg-font-size-large"> </i><span class="wysiwyg-font-size-medium"><span class="wysiwyg-font-size-medium">and held making an angle <span class="wysiwyg-font-size-large"><span class="wysiwyg-font-size-large">$60^{0}$ <span class="wysiwyg-font-size-medium"><span class="wysiwyg-font-size-medium">with the direction of the field. When the magnet is released, the kinetic energy of the magnet in the equilibrium position is:</p>
Question 507 :
An electron has mass $9 \times 10^{-31}kg$ and charge $1.6 \times 10^{-19} C$ is moving with a velocity if $10^{6} m/s,$ enters a region where magnetic field exists. If it describes a circle of radius $0.10m$, the intensity of magneticfield must be:
Question 508 :
Due to a small magnet, intensity at a distance x in the end on position is $9$ gauss. What will be the intensity at a distance $\dfrac{x}{2}$ on broad side on position.
Question 509 :
The magnetic field in a region is given by B=$\dfrac{B_0}{L}$y(k) where L is a fixed length. A conducting rod of length L lies along the Y-axis between the origin and the point (0.L,0). If the rod moves with a velocity v=$v_0$i, find the emf induced between thee ends of the rod.
Question 510 :
There are two current carrying planar coils each made from identical wires of length L. $C_1$ is circular (radius R) and $C_2$ is square(side a). They are so constructed that they have same frequency of oscillation when they are place in the same uniform magnetic field $\vec{B}$ and carry the same current. Find a in terms of R.
Question 511 :
A magnetizing field of 1600A/m producers a magnetic flux of 2 x $10^{-5}$ Wb in a bar of iron of cross section 0.2 x $10^{-4}m^2$. Calculate the susceptibility of the bar.
Question 512 :
Charge Q is uniformly distributed on a thin insulating ring of mass m which is initially at rest. To what angular velocity will the ring be accelerated when a magnetic field B, perpendicular to the plane of the ring, is switched on?<br><br>
Question 513 :
A short magnet is arranged with its axis along east-west. A compass box is placed on its axial line at a distance of $20\ cm$ from centre. If the deflection is $45$. Find moment of magnet $(B_{H} = 0.4\times 10^{-4}T)$.
Question 514 :
A specimen of iron is uniformly magnetised by a field of $500Am^{-1}$. If the magnetic induction in the specimen is $0.2 Wbm^{-2}$, susceptibility is :
Question 515 : <span class="wysiwyg-font-size-medium"><span class="wysiwyg-font-size-medium"><p class="wysiwyg-text-align-left">The least value of magnetic moment (where $m$ is the mass of the electron, $e$ is the charge of electron) is :<br/></p>
Question 517 :
Every iron atom in a ferromagnetic domain in iron has a magnetic dipole moment equal to $9.27 \times 10^{-24} \ A-m^2$. A ferromagnetic domain in iron has the shape of a cube of side $1 \mu m$. The maximum dipole moment occurs when all the dipoles are aligned. The molar mass of iron is $55 \ g$ and its specific gravity is $7.9$. The magnetisation of the domain is:
Question 518 :
A magnetic needle suspended by a silk thread is vibrating in the earth's magnetic field. If temperature of the needle is increased to $1000^0C$, then
Question 519 :
In a vertical plane $p_1$ making angle $30^o $ with magnetic meridian, apparent angle of dip in vertical plane $p_2 $ is $60^o$ , which is perpendicular to plane $p_1$ is:
Question 520 :
A planar coil of area 7 $\mathrm{m}^{2}$ carrying an anti-clockwisecurrent 2 A is placed in an extemal magnetic field $\vec{B}=(0.2\hat{i}+0.2\hat{j}-0.3\hat{k})$, such that the normal to the plane is along the line$(3\hat{i}-5\hat{j}+4\hat{k})$. Select correct statements from the following . ( Consider Normal of the coiland Magnetic moment vectors to be inthe same direction )<br>
Question 522 :
The period of a magnet in earth's field $B_0$ is $T$. When another magnet is placed at certain distance on the magnetic meridian in the same line as the centre of the vibrating magnet, the period is $T_1$. When the magnet in the same position is reversed the period is $T_2$. [The field due to the magnet is smaller than the earth's horizontal component]. Then the field due to the magnet at the centre of the vibrating magent?
Question 523 :
Assertion : Lenz's Law violates the principle ofconservation of energy<br>Reason : Induced emf always opposes thechange in magnetic flux responsible for itsproduction.<br>
Question 524 :
In a region of uniform magnetic induction $B = 10^{-2}tesla$, a circular coil of radius 30 cm and resistance $\pi^2$ ohm is rotated about an axis, which is perpendicular to the direction of B and which forms a diameter of coil. If the coil rotates at 200 r.p.m., the amplitude of alternating current induced in the coil is :-
Question 525 :
Statement-1: The core of the transformer is laminated to avoid loss of energy.<br>Statement-2: A laminated metal sheet placed in a changing magnetic field has lower eddy current.
Question 526 :
A short magnet when placed at a distance of $15cm$ in $Tan$ $A$ position produces ${60}^{o}$ deflection. If the magnet is cut into 3 equal parts and one of them is kept at the same distance in $Tan$ $A$ position, the deflection is:
Question 528 : <p>If a magnet of pole strength m is divided into four parts such that the length and width of each part is half that of the initial one, then the pole strength of each part will be</p>
Question 529 :
Three magnets of the same length but moments M, $2$M and $3$M are arranged in the forms of an equilateral triangle with opposite pole nearer, the resultant magnetic moment of the arrangement is?
Question 530 :
The tangent drawn at any point on the magnetic lines of force gives direction of mangetic field at that point.<br/>
Question 531 :
A thin conducting rod of length $l$ is moved such that its end $B$ moves along the X-axis while end $A$ moves along the Y-axis. A uniform magnetic field $B = {B_0}\hat k$ exists in the region. At some instant,the velocity of end $B$ is $v$ and the rod makes an angle of $\theta = 60$ with the X-axis as shown in the figure. Then, at this instant<br>
Question 532 :
The ratio of magnetic fields due to a bar magnet at the two axial points $P_1$ and $P_2$ which are separated from each other by $10$cm is $25:2$. Point $P_1$ is situated at $10$cm from the centre of the magnet.Points $P_1 $and $ P_2$ are on the same side of magnet and distance of $P_2$ from the centre is greater than distance of $P_1$ from the centre of magnet,then magnetic length is
Question 533 :
A rod of ferromagnetic material with dimension $10 \times 0.5 \times 0.2  cm^3$ is placed in a magnetic field of strength $0.5 \times 10^4  Am^{-1}$ as a result of which a magnetic field of $5 Am^{-2}$ is produced in the rod. The value of magnetic induction will be
Question 534 :
Ratio of maximum to minimum intensity is 25:16.Calculate ratio of intensities:-
Question 535 :
If a dip circle is placed in a vertical plane at an angle of $30^{\underline{o}}$ to the magnetic meridian, the dip needle makes an angle of $45^{\underline{o}}$ with the horizontal. The real dip at that place is?
Question 536 :
A circular loop has a radius $10\ cm$ and is carrying a current of $0.1\ A$. Its magnetic moment is ______<br>
Question 537 :
A permanent magnet has shape of a thin disc with magneticmoment along its axis the radius of the disc is 1 cm. The magnetic field due to it can be assumed to be that due to a molecular current I flowing along the rim of the disc. It $\bar B$ at a distance of 10 cm from its centre on the axis is 30$\mu$T, find I (approximately).
Question 538 :
A metal wire of mass $m$ slides without friction on two rails at distance $d$ apart. The track is in a vertical uniform field of induction$\vec B.$ A constant current$\vec i$ flows along one rail across the wire and back down the other rail the velocity of the wire as a function of time, assuming it to be at rest initially.<br>
Question 539 :
An electron having mass $9.1\times 10^{-31}$ kg, charge $1.6\times 10^{-19}$C and moving with the velocity of $10^6$ m/s enters a region where magnetic field exists. If it describes a circle of radius $0.2$m then the intensity of magnetic field must be ___________$\times 10^{-5}$T.
Question 540 :
A compass needle free to turn in a horizontal plane is placed at the centre of a circular coil of $30$ turns and radius $12$cm. The coil is in a vertical plane making an angle of $45^o$ with the magnetic meridian when the current in the coil is $0.35$A, the needle points west to east. Determine the horizontal component of earth's magnetic field at the location.
Question 541 :
The coercivity of a magnet is $3\times 10^{3}Am^{-1}$. What current should be passed through a solenoid of length $10\ cm$ and number of turns $50$ that the magnet is demagnetized when inserted in it?
Question 542 :
Dip circle is not set into magnetic meridian and the angle at which it is inclined to the magnetic meridian is unknown. $\delta'$ and $\delta''$ are apparent dips at a place in which dip circle is kept in transverse positions. The dip is:
Question 543 :
If relative permeability of iron is 2000. Its absolute permeability in S.I. units is
Question 544 :
Assertion: Induced potential across a coil and therefore induced current is always opposite to the direction of current due to external source.
Reason: Lenz's law states that induced emf always opposes the cause due to which it is being produced.
Question 545 : <p class="wysiwyg-text-align-left"><span class="wysiwyg-font-size-medium"><span class="wysiwyg-font-size-medium">Each atom of an iron bar ($5 m\times 1m \times 1m$) has a magnetic moment $1.8\times 10^{-23}A-m^{2}$. Knowing that the density of iron is $7.78\times 10^{3}kgm^{-3}$, atomic weight is $56$ amu and avogadro's number is $6.02\times 10^{23}$. The magnetic moment of bar in the state of magnetic saturation will be :<br/></p>
Question 546 :
The magnetic moment of a dipole is 2 Am$^{2}$. Magnetic induction in air at a distance of 10 cm from the dipole on a line making an angle of $60^{0}$ with the axis of dipoles is :<br/>
Question 547 :
The time period of a freely suspended magnet is $4$s. If it is broken in length into two equal parts and one part is suspended in the same way. Then its time period will be.
Question 548 : <span class="wysiwyg-font-size-medium"><span class="wysiwyg-font-size-medium"><p class="wysiwyg-text-align-left">A dip circle is set such that the dip needle moves freely in the magnetic meridian. In this position, the angle of dip is 39$^{0}$. Now the dip circle is rotated so that the plane in which the needle moves makes an angle of 30$^{0}$ with the magnetic meridian. In this position ,the needle will dip by an angle :<br/></p>
Question 549 :
Two magnets of moments $8$ and $125$ units are placed so as to have a common axial line and like poles faing each other. Then the distances of the centres of the magnets from the null point will be :
Question 550 :
Two streams of electrons are moving parallel to each other in the same direction. They_____<br/>
Question 552 :
<strong>A galvanometer in series with a high resistance is called </strong><br>
Question 553 :
The magnetic field normal to a coil of 40 turns area $ 3 cm^2 $ is B = (250 - 0.6t) millitesla. The emf induced in the coil will be
Question 554 :
The force of repulsion between two parallel wires is $f$ when each one of them carries a certain current I. If the current in each is doubled, the force between them would be
Question 555 :
How will crowding the wires of a solenoid, more closely together, will affect the strength of the field inside it?<br/>
Question 559 :
Why does toroid have a higher magnetic field than a solenoid?
Question 560 :
A circular coil of wire is connected to a battery of negligible internal resistance and has magnetic induction $B$ at its centre. If the coil is unwound and rewound to have double the number of turns, and is connected to the same battery, then the magnetic induction at the center is :<br/>
Question 562 :
The sensitiveness of a moving coil galvanometercan be increased by decreasing<br>
Question 564 :
The time period of a charged particle undergoing a circular motion in a uniform magnetic field is independent of its
Question 565 :
A current I is passed through a solenoid of n turns per unit length. What is the magnetic filed inside the solenoid ? <br/>
Question 566 :
By inserting a soft iron piece into a solenoid, strength of the magnetic field
Question 567 :
When a current carrying coil is placed in a uniform magnetic field of induction $B$, then a torque $\tau $ acts on it. If $I$ is the current, $n$ is the number of turns and $A$ is the face area of the coil and the normal to the coil makes an angle $\theta $ with $B$, Then<br/>
Question 568 :
The strength of the magnetic field of solenoid increases with the decrease in number of turns in the solenoid.<br><br>
Question 569 :
The restoring couple in the moving coil galvanometer is due to<br/>
Question 572 :
The current that must flow through the coil of a galvanometer so as to produce a deflection of one division on its scale is called<br>
Question 573 :
We have a galvanometer of resistance 25$\Omega$. It is shunted by a 2.5$\Omega$ wire, the part of total current that flows through the galvanometer is given as:
Question 575 :
Complete the following statements with an appropriate word / term to be filled in the blank space(s).<br/><br/>Magnetic field lines emerge from the _________ pole of a solenoid or a permanent magnet.<br/>
Question 577 :
When an electric current passes through a solenoid, the distance between any two adjacent rings of the solenoid _____.
Question 578 :
In which  form  the field lines inside the infinite solenoid are present ?<br/>
Question 579 :
A moving coil type of galvanometer is basedupon the principle that<br>
Question 580 :
In ballistic galvanometer, the frame on which the coil is wound is non-metallic to:
Question 581 :
In cyclotron, radius of circular path traced by positive ions is ____________.
Question 582 :
In cyclotron, for a given magnet, radius of the semicircle traced by positive ion is directly proportional to__________. (v=velocity of positron ion)<br/>
Question 583 :
A coil of area $A$, turns $N$ and carrying current $i$ is placed with its face parallel to the lines of magnetic induction $B$. The work done in rotating the coil through an angle of $180^{0}$ is<br/>
Question 584 :
Which of the following is based on mechanical effect of electric current?
Question 585 :
To make the magnetic field radial in a moving coil galvanometer:-
Question 586 :
The coil of the moving coil galvanometer is wound over an aluminium frame<br/>
Question 587 :
The magnetic field of a solenoid carrying a current is similar to that of a
Question 589 :
If 6 mm is the distance moved by the thimble on the main scale for 6 rotations then pitch of the screw is :<br>
Question 590 :
Ina moving coil galvanometer, deflection of thecoil is related to the electrical current $i$bytherelation<br>
Question 592 :
A large solenoid of windings of 400 turns per meter carries a current 5A. The magnetic field at the centre of the solenoid is about:
Question 594 :
How much length of a very wire is required to obtain a solenoid of length $I_0$ and inductance L :
Question 595 :
A long solenoid has magnetic field strength of $3.14\times 10^{-2}\ T$ inside it when a current of $5\ A$  passes through it. The number of turns in $1\ m$ length of the solenoid is<br/>
Question 596 :
Complete the following sentenceA current carrying solenoid behaves like a $\underline{          }$. 
Question 597 :
If a toroid uses bismuth for its core, the field in the core compared to that in empty core will be slightly
Question 598 :
A small coil of N turns has an area A and a currenti flows through it. The magnetic dipole momentof the coil will be<br>
Question 599 :
Which of the following expressions are applicable to the moving coil galvanometer?
Question 600 :
Assertion: Even Though $\displaystyle \oint_{\mathrm{c}}\vec{\mathrm{B}} \mathrm{d}\overline{l}$ is zero along a closed Amperian loop $\mathrm{C}$, the magnetic field $\overline{\mathrm{B}}$ may not be zero over C.
Reason: $\displaystyle \oint_{\mathrm{s}}\overline{\mathrm{B}}\mathrm{d}\overline{\mathrm{S}}$ is always zero for any closed surface S.
Question 601 :
A helium nucleus makes a full rotation in a circle of radius $0.8 m$ in $2 sec$. The value of the magnetic field induction $B$ in tesla at the centre of circle will be<br>
Question 602 :
The force between two parallel conductors, each of length $50 m$ and distant $20 cm$ apart, is $1 N$. If the current in one conductor is double than that in another one, then their values will respectively be :<br/>
Question 603 :
A proton and an $\alpha $ -particle enter a uniform magnetic field perpendicularly with the same speed. If proton takes 25 $\mu$ second to make 5 revolutions, then times period for the $\alpha$-particle would be
Question 604 :
A current $I=1.00\:A$ circulates in a round thin-wire loop of radius $R=100\:mm$. Find the magnetic induction at the point lying on the axis of the loop at a distance $x=100\:mm$ from its centre.
Question 605 :
An electron having momentum 2.4 X $10^{-23}$kg m $s^{-1}$ enters a region of uniform magnetic field of 0.15 T. The field vector makes an angle of $30^0$ with the initial velocity vector of the electron. The radius of the helical path of the electron in the field shall be :
Question 606 :
In Bohr atomic model an electron is revolving round the nucleus in a circular path of radius $5.1 \times10^{-11}$ <br> $m$ with a frequency $6.8 \times10^{15}$cycles/sec. The magnetic induction at the center of the orbit will be :<br/>(Given charge on electron $e=1.6\times 10^{-19}C$)<br/>
Question 607 :
Consider the motion of a positive point charge in a region where there are simultaneous uniform electric and magnetic fields $\overrightarrow{E} = E_{0}\hat{j}$ and $\overrightarrow{B} = B_{0}\hat{j}$. At time t = 0, this charge has velocity $\overrightarrow{v}$ in the x-y plane, making an angle $\theta$ with the x axis.<br>Which of the following option(s) is(are) correct for time t > 0 ?<br><span id="_wysihtml5-undo" class="_wysihtml5-temp"><br>
Question 608 :
Assertion: The magnetic field produced by a current carrying solenoid Is independent of its length and cross-sectional area.
Reason: The magnetic field inside the solenoid is uniform.
Question 609 :
The distance between the wires of electric mains is 12cm. These wires exprience 4 mgwt per unit length. The value of current flowing in each wire will be if they carry current in same direction<br/><br/>
Question 610 :
A solenoid has a core of a material with relative permeability of $500$. The windings of the solenoid are insulated from the core and carry a current of $2$A. If the number of turns is $1000$ per meter, then magnetisation is?
Question 611 :
Assertion: The energy of a charged particle moving in a uniform magnetic field does not change.
Reason: Work done by magnetic field on the charge is zero.
Question 612 :
The value of intensity of magnetic field at a point due to a current carrying conductor depends<br>
Question 613 :
A coil of $N$ turns and area $A$ is rotated at the rate of $n$ rotations per second in a magnetic field of intensity $B$, the magnitude of the maximum magnetic flux will be :
Question 614 :
The magnetic induction at a point distance $X$ from the centre, on the axis of a circular current carrying coil is inversely proportional to (if $X>>$ radius of coil) <br/>
Question 615 :
A bar magnet has coercivity $ 4 \times 10^3 Am^{-1} $.It is desired todemagnetise it by inserting it inside a solenoid $12 cm $ long andhaving $60 $ turns. The current that should be sent through thesolenoid is
Question 616 :
A coil of one turn is made of a wire of certain length and then from the same length a coil of two turns is made. If the same current is passed in both the cases, then the ratio of the magnetic inductions at their centres will be :<br/>
Question 618 :
The expression for the torque acting on a coil having area of cross-section $A$, number of turns $n$, placed in a magnetic field of strength $B$, making an angle $\theta$ with the normal to the plane of the coil, when a current $i$ is flowing in it, will be
Question 619 :
The maximum energy of a deuteron coming out a cyclotron is $20\ MeV$. The maximum energy of proton that can be obtained from this accelerator is:
Question 620 :
A proton, a deuteron and an $\alpha $ particle are accelerated through same potential difference and then they enter in a normal uniform magnetic field, the ratio of their kinetic energies will be:<br/>
Question 622 :
A charged particle, moving at right angle to a uniform magnetic field, starts moving along a circular arc of radius of curvature $r$. In the field it now penetrates a layer of lead and loses ${\dfrac{3}{4} }^{th}$ of it's initial kinetic energy. The radius of curvature of it's path now will be :<br/>
Question 623 :
An electron and a proton are injected into a uniform magnetic field perpendicular to it in the same direction. If electron and proton have same kinetic energy then the radius of curvature is 
Question 624 :
A coil of area $100\ cm^{2}$ having $500$ turns carries a current of $1\ m A$. It is suspended in a uniform magnetic field of induction $10^{-3}Wb /m^{2}$ . It's plane makes an angle of $60^{o}$ with the lines of induction. The torque acting on the coil is :<br/>
Question 625 :
Each of the following particles is projected with the same speed into a uniform magnetic field $B$ such that the particle's initial velocity is perpendicular to $B$. Which one would move in a circular path with the largest radius?A particle is projected at a given speed into a uniform magnetic field B and perpendicular to it. Choose the particle that will have the largest radius.
Question 626 :
A circular coil of wire of radius $r$ has $n$ turns and carries a current $l$. The magnetic induction ($B$) at a point on the axis of the coil at a distance $\sqrt{3}r$ from its centre is<br/>
Question 627 :
A beam of ions enters normally into a uniform magnetic field of $4 \times 10^{-2}$ tesla with velocity of $2 \times 10^5 m/s$. If the specific charge of the ion is $5 \times 10^7 C/kg$, then the radius of the circular path described will be:
Question 628 :
Two circular coils are made of two identical wires of the same length. If the number of turns of the two coils are 4 and 2, then the ratio of magnetic inductions at the centres will be:
Question 629 :
Two long parallel copper wires carry currents of $5A$ each in the opposite direction . If the wires areseparated by a distance of $0.5 m$, then the forcebetween the two wires is<br><br>
Question 630 :
A current carrying long solenoid is placed on the ground with its axis vertical. A proton is falling along the axis of the solenoid with a velocity $v$. When the proton enters into the solenoid, it will
Question 631 :
The distance between two parallel wires carrying current of $1A$ is $1m$. The force per unit length between the conductors is<br/>
Question 632 :
Two wires carrying current in opposite directions are placed a distance $a$ apart.<br>Which of the following will cause the greatest increase in the magnitude of the force between the wires?
Question 633 :
Assertion: There is no change in the energy of a charged particle moving in a magnetic field although a magnetic force is acting on it.
Reason: Work done by centripetal force is always zero.
Question 634 :
The AC voltage across a resistance can be measured using a<br>
Question 635 :
A long solenoid of length $L$ has a mean diameter $D$. It has $n$ layers of winding of $N$ turns each. If it carries a current $I$, the magnetic field at its centre will be.<br>
Question 636 :
A charged particle enters a magnetic field at right angles to the field. The field exists for a length equal to 1.5 times the radius of circular path of particle. The particle will be deviated from its path by :<br/>
Question 637 :
" On flowing current in a conducting wire the magnetic field produces around it". It is a law of
Question 638 : Match the following and find the correct pairs:<br/><table class="wysiwyg-table"><tbody><tr><td>List I</td><td>List II</td></tr><tr><td>(a) Fleming's left hand rule</td><td>(e) Direction of induced current</td></tr><tr><td>(b) Right hand thumb rule</td><td>(f) Magnitude and direction of magnetic induction</td></tr><tr><td>(c) Biot-Savart law</td><td>(g) Direction of force due to magnetic induction</td></tr><tr><td>(d) Fleming's right hand rule</td><td>(h) Direction of magnetic lines due to current</td></tr></tbody></table>
Question 639 :
Two concentric coils, each of radius equal to $2\pi\ \text{cm}$, are placed at right angles to each other. Currents of $3\ \text{A}$ and $4\ \text{A}$, respectively, are flowing through the two coils. The magnetic induction, in $\text{Wb}\ \text{m}^{-2}$, at the center of the coils will be<br>$[{\mu}_{0}=4\pi \times {10}^{-7}\ \text{Wb}$ $({Am}^{-1})]$<br>
Question 640 :
There are $50$turns of a wire in every cm length of a long solenoid.If $4\ A$currents is following in the solenoid,the approximate value of magnetic field along its axis at an internal point and at one end will be respectively.
Question 641 :
Two parallel straight conductors, in which current is flowing in the same direction, attract each other. The cause of it is<br>
Question 642 :
A charged particle (charge q) is moving in a circle of radius R with uniform speed v. The associated magnetic moment $\mu$ is given by
Question 643 :
Two long, thin, parallel conductors, separated by a distance d carry currents $i_1$ and $i_2$. The force acting on unit length of any one conductor is F :<br/>
Question 645 :
The magnetic field of a given length of wire carrying a current for a single turn cicular coil at center is B, then its value for two turns for the same wire when same current passing through it is
Question 646 :
A circular current carrying coil has a radius $R$. The distance from the centre of the coil on the axis where the magnetic induction will be $\left (\dfrac {1}{8}\right )^{th}$ of its value at the centre of the coil is<br>
Question 647 :
What should one do to maximize the magnitude of the magnetic force acting on a charged particle moving in a magnetic field?<br>I. Maximize the strength of the magnetic field<br>II. Minimize the particles velocity<br>III. Ensure that the particle is moving in the same direction as the magnetic field lines.
Question 648 :
The magnetic field due to current carrying loop of radius $3cm$ at a point on the axis at a distance of $4$ cm from the centre is $54\mu $ T. Its value at the centre of the loop is :<br/>
Question 649 :
A solenoid 1.5 m long and 4.0 cm in diameter possesses 10 turns/ cm. A current of 5 A is flowing through it. Then the magnetic induction (i) inside and (ii) at one end on the axis of solenoid are respectively 
Question 650 :
A particle of charge $q$ and mass $m$ starts moving from the origin under the action of an electric field $\overrightarrow{E}=E_o\hat{i}$ and $\overrightarrow{B}=B_0\hat{i}$ with a velocity $\overrightarrow{v}=v_0\hat{j}$. The speed of the particle will become $2v_0$ after a time<br>
Question 651 :
Assertion: A charged particle moves along positive y-axis with constant velocity in uniform electric and magnetic fields.If magnetic field is acting along positive x-axis,then electric field should act along positive z-axis.
Reason: To keep the charged particle undeviated the relation $\vec{E}=\vec{B}\times \vec{v}$ must hold good.
Question 653 :
An electron of charge e and mass m is moving in circular path of radius r with a uniform angular speed . Then which of the following statements are correct?
Question 654 :
A coil having $N$ turns is wound tightly in the formof a spiral with inner and outer radii a and brespectively. When a current i passes throughthe coil,the magnetic field at the centre is<br>
Question 655 :
A long solenoid has $200$ turns per $cm$ and carries a current of $2.5\ Amp$. The magnetic field at its centre is ($\mu _{0}=4\pi \times 10^{-7} $Wb/ A-m)
Question 656 :
Two circular coils P and Q are made from similar wire, but radius of Q is twice that of P. What should be the value of potential difference across them so that the magnetic induction at their centre may be same?
Question 657 :
z-coordinate of the particle as a function of time after the magnetic field is switched on is<br>
Question 658 :
An electron beam passes through a magnetic field of $2\times 10^{-3}Wb/m^2$ and an electric field of $1.0\times 10^4 V/m$ both acting simultaneously. The path of electron remains undeviating. The speed of electron if the electric field is removed, and the radius of electron path will be respectively.<br>
Question 659 :
The earth's magnetic field at a given point is $0.5\times 10^{-5}Wb m^{-2}$. This field is to be annulled by magnetic induction at the centre of a circular conducting loop of radius $5.0$cm. The current required to be flown in the loop is nearly <br>
Question 660 :
Three particles, an electron $(e),$ a proton $(p)$ and a helium atom $(He)$ are moving in circular paths with constant speeds in the $x-y$ plane in a region where a uniform magnetic field $B$ exists along z-axis. The times taken by $e, p$ and $He$ inside the field to complete one revolution are $t_e, t_p$ and $t_{He}$ respectively. Then :<br>
Question 663 :
A circular coil is made from a wire of length $2m$ . Its radius is $\dfrac{4}{\pi} cm$. When a current of $1A$passes through it, its magnetic moment is
Question 664 :
An oil drop of mass 0.2 mg has lost 100 electrons. The density of oil is 0.8 g/cc. Find the electrostatic pressure it has.<br/>
Question 665 :
An alternating electric field of frequency 'y' is applied across the dees (radius R) of a cyclotron to accelerate protons (mass m). The operating magnetic field 'B' used and K.E. of the proton beam produced by it are respectively (e = charge of proton).
Question 666 :
Two galvanometers $A$ and $B$ require $3 mA$ and $6 mA$ respectively, to produce the same deflection of $10$ divisions. Then is,
Question 667 :
A charged particle of unit mass and unit charge moves with velocity $\vec{v}=(8\hat{i}+6\hat{j})m/s$ in a magnetic field of $\vec{B}=2\hat{k} T$. Choose the correct alternative(s).
Question 668 :
The magnetic field normal to the plane of a wire of n turns and radius r which carries a current i is measured on the axis of the coil at a small distance h from the centre of the coil. This is smaller than the magnetic field at the centre by the fraction
Question 669 :
A doubly ionized $He^{+2}$ atom travels at right angles to a magnetic field of induction $0.4 T$ at a velocity of $10^{5}m/s$ describing a circle of radius $r$. A proton traveling with same speed in the same direction in the same field will describe a circle of radius : <br/>
Question 670 :
A charged particle is moving along positive y-axis in uniform electric and magnetic fields<br/>             $\vec{E}={E}_{o}\hat{k}$   and   $\vec{B}={B}_{o}\hat{i}$Here ${E}_{o}$ and ${B}_{o}$ are positive constants.Choose the correct options.
Question 671 :
Two long thin parallel conductor are kept very close to each other without  touching. One carries a current $i$ and the other has charge $\lambda$ per unit length. An electron moving parallel to the conductor is undeflected. lf  $c$ is the velocity of light. then :<br/>
Question 672 :
When a proton is released from rest in room, it starts with an initial acceleration ${ a }_{ 0 }$ towards west When it is projected towards north with a speed ${ V }_{ 0 }$ it moves with an initial acceleration ${ 3a }_{ 0 }$ towards west. The electric and magnetic fields in the room are :
Question 673 :
The magnetic induction due to circular current-carrying conductor of radius $a$, at its centre is $B_c$. The magnetic induction on its axis at a distance $a$ from its centre is $B_a$. The value of $B_c : B_a$ will be :<br/>
Question 674 :
A proton and a deuteron ion having the same kinetic energies enter a region of uniform magnetic field perpendicularly. Deuteron's mass is twice that of proton. Calculate the ratio of the radii of their circular paths.
Question 675 :
A solenoid of $0.4 m$ length with $500$ turns carries a current of $3 A$. A coil of $10$ turns and of radius $0.01 m$ carries a current of $0.4 A$. The torque required to hold the coil with its axis at right angles to that of solenoid in the middle point of it is:
Question 676 :
The current sensitivity of a moving coil galvanometer increases by $20\%$ when its resistance is doubled. Calculate, by what factor does the voltage sensitivity change?
Question 677 :
When a charged particle moves only electric or a magnetic field, its speed is $v$ and acceleration is $a$
Question 678 :
A particle of mass $1\times {10}^{-26} kg$ and charge $+1.6\times {10}^{-19}C$ travelling with a velocity of $1.28\times {10}^{6}m/s$ along positive direction of x-axis enters a region in which a uniform electric field $\vec{E}$ and a uniform magnetic field $\vec{B}$ are present such that<br/>              ${E}_{z} =-102.4kV/m$<br/>              ${B}_{y}=8\times {10}^{-2}Wb/{m}^{2}$<br/>The particle enters this region at origin at time t=0.Then
Question 679 :
(A) In tangent galvanometer the circular frame is rotated until the plane of the coil is parallel to magnetic meridian<br>(B) In tangent galvanometer current through it is related to deflection of needle as
Question 681 :
Two circular coils of radii 5 cm and 10 cm carry currents of 2 A.The coils have 50 and 100 turns respectively and are placed in such a way that their planes as well as their centres coincide.Magnitude of magnetic field at the common centre of coil is
Question 682 :
A photon of energy E ejects a photoelectron from a metal surface whose work function is $W_0.$ If this electron enters into a uniform magnetic field of induction B in a direction perpendicular to the field and describes a circular path of radius r, then the radius r is given by (in the usual notation)
Question 683 :
An electron accelerated through a potential difference $V$ passes through a uniform transverse magnetic field and experiences a force $F$. If the accelerating potential is increased to $2V$, the electron in the same magnetic field will experience a force :
Question 684 :
Two particles $A$ and $B$ having equal charges $+6$ C after being accelerated through the same potential difference enter in a region of uniform magnetic field and describe circular paths of radii $2 cm$ and $3 cm$ respectively. The ratio of mass of $A$ to that of $B$ is :
Question 685 :
 A  cyclotron accelerates deuterons to $16 MeV$ energy. lf deuterium is replaced by helium what will be the energy of alpha particles?<br/>
Question 686 :
The field normal to the plane of wire of $n$ turns and radius $r$ which carries a current $i$ is measured on the axis at a small distance $h$ from the centre of the coil. This is smaller than the field at the centre by the fraction
Question 687 :
A long wire carries a current of $20\ A$ long the axis of a solenoid, the field due to the solenoid is $4\ mT$. The resultant field at a point $3\ mm$ from the solenoid axis is :
Question 688 :
Two particles of equal charges after being accelerated through the same potential difference enter in a uniform transverse magnetic field and describe circular paths of radii $R_1$ and $R_2$. Then the ratio of their respective masses $(M_1/ M_2)$ is
Question 689 :
In a mass spectrometer used for measuring the masses of ions, the ions are initially accelerated by an electric potential $V$ and then made to follow semicircular paths of radius $R$ using a magnetic field $B.$ If $V$ and $B$ are kept constant, the ratio $\left(\dfrac{charge \  on \  the \  ion}{mass \  of \  the \  ion}\right)$ will be proportional to
Question 690 :
A charged particle moves through a magneticfield in a direction perpendicular to it. Then the
Question 691 :
A solenoid of 0.4 m length with 500 turns carries a current of 3 A. A coil of 10 turns and of radius 0.01 m carries a current of 0.4 A. The torque required to hold the coil with its axis at right angle to that of the solenoid in the middle part of it, is:
Question 692 :
An electron $($mass $=9.1\times 10^{-31}$; charge $=-1.6\times 10^{-19}\mathrm{C})$ experiences no deflection if subjected to an electric field of $3.2\times 10^{5}\mathrm{V}/\mathrm{m}$ and a magnetic field of $2.0\times 10^{-3}\mathrm{W}\mathrm{b}/\mathrm{m}^{2}$. Both the fields are normal to the path of electron and to each other. Ifthe electric field is removed, then the electron will revolve in an orbit of radius :<br>
Question 693 :
Assertion: A soft iron core is used in a moving coil galvanometer to increase the strength of magnetic field.
Reason: From soft iron more number of the magnetic lines of force passes.
Question 694 :
In a region,steady and uniform electric and magnetic fields are present.These two fields are parallel to each other.A charged particle is released from rest in this region.The path of the particle will be :<br/>
Question 695 :
A current of i ampere is flowing in an equilateral triangle of side a. The magnetic induction at the centroid will be?
Question 696 :
A battery is connected between two points A and B on the circumference of a uniform conducting ring of radius r and resistance R. One of the arcs AB of the ring subtends an angle $\theta$ at the centre. The value of the magnetic induction at the centre due to the current in the ring is
Question 697 :
A charged particle goes undeflected in a region containing electric and magnetic fields. It is possible that<br>
Question 698 :
The field normal to the plane of wire of n turns and radius r which carries a curent i is measured on the axis at a small distance h from the center of the coil. This is smaller than the field at the centre by the fraction:<br/><br/>
Question 699 :
Two circular coil $1$and $2$are made from thesame wire but the radius of the $1st$coil is twicethat of the $2nd$coil. What potential difference involts should be applied across them so that themagnetic field at their centres is the same-
Question 700 :
Alternating current is flowing in inductance L and resistance R. The frequency of source is $\displaystyle\frac{\omega}{2\pi}$. Which of the following statement is correct.
Question 701 :
Which of the following does not have the same dimensions as the Henry?
Question 702 :
Two concentric co-planar circular loops of radii $r_1$ and $r_2$ carry currents of respectively $i_1$ and $i_2$ in opposite directions (one clockwise and the other anticlockwise.) The magnetic induction at the centre of loops is half that due to $i_1$ alone at the centre. If $r_2 = 2r_1$. the value of $i_2 / i_1$ is
Question 704 :
If circular coil with $N_{1}$ turns is changed in to a coil of $N_{2}$ turns. What will be the ratio of self inductances in both cases.
Question 705 :
Henry, the SI unit of inductance can be written as :
Question 706 :
Multiple Correct Answers Type<br>The SI unit of inductance, henry, can be written as
Question 708 :
When the number of turns in a solenoid is doubled without any change in the length of the solenoid, its self-inductance becomes :
Question 709 :
A student measures the terminal potential difference (V) of a cell (of emf $\varepsilon$ and internal) resistance r) as a function of the current (I) flowing through it. The slope and intercept of the graph between V and I, then respectively equal to :<br><br><br><br>
Question 711 :
Two coils A and B have 200 and 400 turns respectively. A current of 1 A in coil A causes a flux per turn of $10^{-3}$ Wb to link with A and a flux per turn of $0.8 \times 10^{-3}$ Wb through B. The ratio of self-inductance of A and the mutual inductance of A and B is :
Question 712 :
In a transformer, coefficient of mutual inductance between primary and secondary coil is 0.2 H. When current changes by 5 Na in the primary, then: the induced era in the secondary will be
Question 713 :
Two coils $X$ and $Y$ are placed in a circuit such that a current changes by $3\ A$ in coil $X$ and magnetic flux changes of $1.2\ Wb$ occurs in $Y$. The value of mutual inductance of the coils is :<br/>
Question 714 :
In mutual induction<br>A: when current in one coil increases, induced current in neighbouring coil flows in the opposite direction<br>B: When current in one coil decreases, induced current in neighbouring coil flows in the opposite direction
Question 715 :
In case of all flux from the current in coil 1 links with coil2, the coefficient of coupling will be
Question 716 :
An inductor of inductance $100\ mH$ is connected in series with a resistance, a variable capacitance and an AC source of frequency $2.0\ kHz$; The value of the capacitance so that maximum current may be drawn into the circuit.
Question 717 :
If ‘N’is the number of turns in a coil, the value of self inductance varies as <br/>
Question 718 :
The average self-induced emf in a $25 m H$ solenoid when the current in it falls from $0.2 A$ to $0 A$ in $0.01$ second, is <br/>
Question 719 :
The coefficient of self inductance and the coefficient of mutual inductance have <br/>
Question 720 :
A varying current in a coil change from $10A$ to $0$ in $0.5$sec. If the average emf induced in the coil is $220V$, the self inductance of the coil is :<br/>
Question 723 :
In one second, a current of 10 A changes through a coil. The induced emf is 10V, then, self-inductance of the coil is
Question 724 :
The self-inductance of a long solenoid carrying current is independent of:
Question 725 :
When current flowing in a coil changes from $3A$ to $2A$ is one millisecond, $5\ volt$ emf is induced in it. The self-inductance of the coil will be
Question 726 :
A circular coil has $500$ turns of wire and its radius is $5cm$. The self inductance of the coil is:-
Question 727 :
When the number of turns in a coll is doubled without any change in the length of the coll, its self-inductance becomes
Question 728 :
A coil has self inductance of $0.01H$. The current through it is allowed to change at the rate of $1A$ in $10^{-2}$s. The induced emf is<br/>
Question 729 : <p>An airplane in which the distance between the tips of the wings is<b> 50 meter</b> is flying horizontally with a speed of <b>360 km/hour</b> over a place where the vertical component of earths magnetic field is $2.0 \times {10^{ - 4}}Testa.$ The potential difference between the tips of the wings would be:-</p>
Question 730 :
Assertion(A): The possibility of an electric bulb fusing is higher at the time of switching on and off.<br/>Reason(R): Inductive effects produce a large current at the time of switch-on and switch-off. <br/>
Question 731 :
Two coils A and B have mutual inductance $2\times 10^{-2}$ henry. If the current in the primary is $i = 5\sin (10\pi t)$ then the maximum value of e.m.f. induced in coil B is:
Question 732 :
The horizontal component of the earth's magnetic field at a place is $3 \times 10 ^ { - 4 } T$and the dip is $\theta$ = $t a n ^ { - 1 }$ (4/3). A metal rod of length 0. 25 m placed in the north-south position is moved at a constant speed of 10 cm/s towards the east. The e.m.f induced in the rod will be:
Question 733 :
When we move a conductor of length l with speed V perpendicular to the magnetic field B the motional emf induced in the conductor will be
Question 734 :
Whenever, current is changed in a coil, an induced e.m.f. is produced in the same coil. This property of the coil is due to<br/>
Question 736 :
Two sources of equal emf are connected to an external resistance R. The internal resistances of two sources are $R_{ 1 }$ and $R_{ 2 }$($R_{ 2 }$>$R_{ 1 }$). If the potential difference across the source having internal resistance $R_{ 2 }$ is zero, then;
Question 737 :
Under what condition will the strength of current in a wire of resistance R be the same for connection is series and in parallel of n identical cells each of the internal resistance r? When
Question 740 :
Assertion(A): An inductor in a D.C. circuit opposes both a steady current and a changing current.Reason(R): Induced emf is generated only when the flux linked with the inductor remains unchanged.<br/>
Question 742 :
Foran inductorcoil $L = 0.04H$ then work done by source to establish a current of 5A in it is:-
Question 745 :
If $0.1J$ of energy is stored for the flow of current of $0.2A$ in an inductor, then its inductance value is:
Question 747 :
If coil is placed perpendicular to field lines then number of lines passing through coil are :
Question 750 :
Assertion: A small magnet takes longer time in falling in a hollow metallic tube without touching the wall.
Reason: There is opposition of motion due to production of eddy currents in metallic tube
Question 751 :
The magnetic field inside a $2mH$ inductor becomes $0.8$ of its maximum value in $20\mu s$ when the inductor is joined to battery. Find resistance of the circuit.
Question 752 :
A conducting rod is moved with a constant velocity $v$ in a magnetic field. A potential difference appears across the two ends
Question 753 :
Two parallel rails of a railway track insulated from each other and with the ground are connected to a millivoltmeter. The distance between the rails is one metre. A train is traveling with a velocity of $72 km/h$ along the track. The reading of the millivoltmeter (in $mV$ ) is :<br/>(Vertical component of the earths magnetic induction is $2\times 10^{-5}T$ )<br/>
Question 754 :
A current-carrying loop is placed in a uniform magnetic field. The torque acting on it depends upon
Question 756 :
An average emf of $20 V$ is induced in an inductor when the current in it is changed from $2.5 A$ in one direction to the same value in the opposite direction in $0.1$ s. The self-inuctance of the inductor is<br/>
Question 757 :
Reactance of a coil is $157\Omega$. On connecting the coil across a source of frequency $100Hz$, the current lags behind e.m.f. by ${ 45 }^{ o }$. The inductance of the coil is _________.
Question 758 :
If emf induced in a coil is $2V$ by changing the current in it from $8A$ to $6A$ in $2\times {10}^{-3}s$, then the coefficient of self induction is
Question 759 :
Alternating current of peak value $\left( \dfrac{2}{\pi} \right )$ ampere flows through the primary coil of the transformer. The coefficient of mutual inductance between primary and secondary coil is 1 henry. The peak e.m.f. induced in secondary coil is<br>(Frequency of a.c. = 50 Hz)
Question 760 :
Assertion: Lenz's law violates the principle of conservation of energy
Reason: Induced emf always opposes the change in magnetic flux responsible for its production.
Question 761 :
A bar magnet is dropped along the axis of copper ring held horizontally. The acceleration of fall is<br/>
Question 762 :
If inductance per unit length for a solenoid near its centre and near the end is denoted by $L_M$ and $L_e$<br>
Question 763 :
The number of turns in a coil of wire of fixed radius is 600 and its self inductance is 108 mH. The self inductance of a coil of 500 turns will be :<br/>
Question 764 :
When an $AC$ signal of frequency $1kHz$ is applied across a coil of resistance $100\Omega$, then the applied voltage leads the current by $45^o$. The inductance of the coil is:<br/>
Question 765 :
A coil of inductance L is carrying a steady current I what is the nature of its stored energy?
Question 766 :
Assertion: Lenz's law violates the principle of conservation of energy.
Reason: Induced emf always opposes the change in magnetic flux responsible for its production.
Question 769 :
A bar magnet is released from rest along the axis of a very long, vertical aluminum tube. After sometime the magnet
Question 770 :
The magnetic induction at any point due to a long straight wire carrying a current is
Question 771 :
Assertion: An induced emf appears in any coil in which the current is changing.
Reason: Self induction phenomenon obeys Faraday's law of induction.
Question 772 :
The area of a circular coil of $2000$ turns is $70cm^2$. The coil is kept normal to the field of $0.3W/m^2$ and rotated through $180^{\circ} $. The emf in volts generated in $1sec$ will be :
Question 773 :
The magnitude of the earth's magnetic field at the north polw is $B_0$. A horizontal conductor of length $l$ moves with velocity v. The direction of v is perpendicular to the conductor. The induced emf is
Question 774 :
Assertion: The self-inductance of a long solenoid is proportional to the area of cross-section and length of the solenoid.
Reason: Self inductance of a solenoid is independent of the number of turns per unit length.
Question 775 :
A coil of resistance $ 400 \Omega$ is placed in a magnetic field. If the magnetic flux $ \phi (Wb)$ linked with the coil varies with time t (sec) as $\Phi = 50 t^2 + 4$<br/>The current in the coil at t = 2 sec is<br/>
Question 776 :
The two rails of a railway track, insulated from each other and the ground, are connected to millivoltmeter. What is the reading of the millivoltmeter when a train passes at a speed of 180 km/hr along the track, given that the vertical component of earth's magnetic field is $0.2\times 10^{-4}wb/m^2$ and rails are separated by 1 metre<br>
Question 777 :
Energy stored in a coil of self inductance $40\,mH$ carrying a steadycurrent of $2\, A$ is
Question 778 :
A circular coil of radius 8 cm, 400 turns and resistance 2$\Omega$ is placed with its plane perpendicular to the horizontal component of the earths magnetic field. It is rotated about its vertical diameter through $180^o$ in 0.30 s Horizontal component of earth magnetic field at the place is $3 x 10^{-5}$ T. The magnitude of current induced in the coil is approximately
Question 779 :
A uniform magnetic field exists in a region given by $\vec { B } =3\hat { i } +4\hat { j } +5\hat { k } $. A rod of length $5m$ along y-axis moves with a constant speed of $1m$ ${s}^{-1}$ along x axis. Then the induced emf in the rod will be
Question 780 :
A horizontal straight wire $20\ m$ long extending from east to west is falling with a speed of $5.0\ m/s$ at right angle to the horizontal component of the earths magnetic field $0.30\times {10}^{-4}\ Wb/{m}^{2}$. The instantaneous value of the e.m.f induced in the wire will be
Question 781 :
If the number of turns and length of the long solenoid are doubled without changing the area, then its self-inductance $L$ will be:<br/>
Question 782 :
The peak value of an alternating emf E given by<br> $ E = E_0 \,cos\, \omega t $<br>is $ 10\,V $ and frequency is $ 50\,Hz $ . At time $ t = (1/600) \,s $ , the instantaneous value of emf is
Question 783 :
Assertion: Lenz's law violates the principle of conservation of energy. <br>Reason: Induced emf always opposes the change in magnetic flux responsible for its production.
Question 785 :
The magnetic flux in a coil of 100 turns increases by $12 \times 10^3$ Maxwell in 0.2 second due to the motion of a magnet. The emf induced in the coil will be
Question 786 :
A straight conductor 0.1 m long moves in a uniform magnetic field 0.1 T. The velocity of the conductor is 5 m/s and is directed perpendicular to the field. The emf induced between the two ends of the conductor is:
Question 787 : Match the following:<br/><table class="wysiwyg-table"><tbody><tr><td>Quantity</td><td>Formula</td></tr><tr><td>1) Magnetic flux linked with a coil</td><td>a) $\displaystyle -N\frac { d\phi  }{ dt } $</td></tr><tr><td>2) Induced emf</td><td>b) $\displaystyle { \mu  }_{ r }{ \mu  }_{ 0 }{ n }_{ 1 }{ n }_{ 2 }{ \pi r }_{ 1 }^{ 2 }l$</td></tr><tr><td>3) Force on a charged particle moving in a electric and magnetic field</td><td>c) $\displaystyle BA\cos { \theta  } $</td></tr><tr><td>4) Mutual inductance of a solenoid</td><td>d) $\displaystyle q\left( \overline { E } +\overline { v } \times \overline { B }  \right) $</td></tr></tbody></table>
Question 788 :
By a change of current from 5 A to 10 A in 0.1s, the self induced emf is 10 V. The change in the energy of the magnetic fieldof a coil will be
Question 789 :
Assertion: An electric lamp is connected in series with a long solenoid of copper with air core and then connected to an ac source. If an iron rod is inserted in the solenoid, the lamp will become dim.
Reason: If an iron rod is inserted in the solenoid, the inductance of the solenoid increases.
Question 790 :
The coefficients of self induction of two inductance coils arc 0.0 1H and 0.03H respectively. When they are connected in series so as to support each other. then the resultant self inductance becomes 0.06 Henry. The value of coefficient of mutual induction will be-<br>
Question 792 :
A square loop of wire, side length 10 cm is placed at angle of $45^{o}$ with a magnetic field that changes uniformly from 0.1 T to zero in 0.7 seconds. The induced current in the loop ( its resistance is $1\Omega$) is
Question 795 :
Two coils have a mutual inductance $0.55H$. The current changes in the first coil according to equation $I={ I }_{ 0 }\sin { \omega t }$.<br>where, ${ I }_{ 0 }=10A$ and $\omega =100\pi { rad }/{ s }$.<br>The maximum value of emf in the second coil is
Question 796 :
A conductor coil moving in a magnetic field produces an induced e.m.f. This is<br/>in accordance with<br/>
Question 797 :
Assertion: Lenzs law violates the principle of conservation of energy.
Reason: Induced e.m.f. always opposes the change in magnetic flux responsible for its production.
Question 798 :
The current passing through a choke coil of $5H$ is decreasing at the rate of $2A/s$. The e.m.f. developed across the coil is
Question 799 :
What is the magnetomotive force (mmf) of a wire with 8 turns carrying three amperes of current?
Question 801 :
Assertion: An emf is induced in a long solenoid by a bar magnet that moves while totally inside the solenoid along the axis of the solenoid.
Reason: As the magnet moves inside the solenoid the flux through individual turns of the solenoid changes.
Question 802 :
The magnetic flux density $B$ is changing in magnitude at a constant rate $dB/dt$. A given mass $m$ of copper, drawn into a wire of radius $a$ and formed into a circular loop of radius $r$ is placed perpendicular to the field $B$. The induced current in the loop is $i$. The resistivity of copper is $\rho$ and density is $d$. The value of the induced current $i$ is
Question 803 :
A plane electromagnetic wave in a non magnetic dielectric medium is given by $\bar{E} = \bar{E_0} ( 4 \times 10^{-7}x - 50 t)$ with distance being in meter and time in seconds. The dielectric constant of the medium is:
Question 804 :
A coil having $n$ turns and resistance $R$ $\Omega$ is connected with a galvanometer of resistance $4R$ $\Omega$. This combination is moved in time $t$ seconds from a magnetic flux $ W_{1}$ to $ W_{2}$. The induced current in the circuit is<br/>
Question 805 :
A circular coil of mean radius of $7$cm and having $4000$ turns is rotated at the rate of $1800$ revolutions per minute in the earth's magnetic field (B$=0.5$ gauss), the peak value of emf induced in coil will be?
Question 806 :
Assertion: Induced potential across a coil and therefore induced current is always opposite to the direction of current due to external source.
Reason: Lenz's law states that induced emf always opposes the cause due to which it is being produced.
Question 807 :
A coil of $n$ turns and radius $r$ is placed in a magnetic field. The electrical power is dissipated due to the current induced in the coil. By stretching the wire, if the number of turns were to be quadrupled and the wire radius halved, the electrical power dissipated would be :<br/>
Question 808 : <p>A coil of area 500 $cm^2$ having 1000 turns is placed such that the plane of the coil is perpendicular to a magnetic field of magnitude $4 \times 10^{-5}$ $weber/m^2$. If it is rotated by 180 about an axis passing through one of its diameter in 0.1 sec, find the average induced emf.</p>
Question 809 :
Assertion : Lenz's Law violates the principle ofconservation of energy<br>Reason : Induced emf always opposes thechange in magnetic flux responsible for itsproduction.<br>
Question 810 :
The magnitude of the earth's magnetic field at the north pole is ${B}_{0}$. A horizontal conductor of length $l$ moves with a velocity $v$. The direction of $v$ is perpendicular to the conductor. The induced emf is
Question 811 :
The uniform magnetic field perpendicular to the plane of a conducting ring of radius $a$ changes at the rate of $\alpha$, then
Question 812 :
The magnetic flux $\phi$ linked with a  conducting coil depends on time as $\phi=4t^n +6$ where n is a positive constant. The induced emf in the coil is e.
Question 813 :
When a coil rotated in magnetic field induced current in it :
Question 814 :
A coil of area $500 cm^2$ having 1000 turns is placed such that the plane of the coil is perpendicular to a magnetic field of magnitude $4 10^{-5} weber/m^2$. If it is rotated by $180$ degree about an axis passing through one of its diameter in $0.1$ sec, find the average induced emf.
Question 815 :
Electric charge $q$ is distributed uniformly over a rod of length $l$. The rod is placed parallel to a long wire carrying a current $i$. The separation between the rod and the wire is $a$. The force needed to move the rod along its length with a uniform velocity $v$ is :<br/>
Question 816 :
A wire in the form of a circular loop of radius $10cm$ lies in a plane normal to a magnetic field of $100T$. If this wire is pulled to take a square shape in the same plane in $0.1s$, find the average induced emf in the loop.
Question 818 :
A conducting metal circular-wire-loop of radius r is placed perpendicular to a magnetic field which varies with time as $B =B_0e^{-t/\tau}$, where $B_0$ and $\tau$are constants, at time t = 0. If the resistance of the loop is R then the heat generated in the loop after a long time $(t \rightarrow \infty)$ is<br>
Question 819 :
A rod of $10cm$ length is moving perpendicular to uniform magnetic field of intensity $5\times { 10 }^{ -4 }Wb/{ m }^{ 2 }$. If the acceleration of the rod is $5m/{s}^{2}$, then the rate of increase of induced emf is _______
Question 820 :
A coil of area $2{m}^{2}$ and resistance $4\Omega$ is placed perpendicular to a uniform magnetic field of $4T$. The loop is rotated by ${90}^{o}$ in $0.1$ second. Choose the correct options
Question 821 :
A rectangular loop of sides $10cm$ and $5cm$ with a cut is stationary between the pole pieces of an electromagnet. The magnetic field of the magnet is normal to the loop. The current feeding the electromagnet is reduced so that the field decreases from its initial value of $0.3T$ at the rate of $0.02T$ ${s}^{-1}$. If the cut is joined and the loop has a resistance of $2.0\Omega$, the power dissipated by the loop as heat is
Question 822 :
A hundred turns of insulated copper wire are wrapped around an iron cylinder of area $1 \times 10^{-3}m^2$ and are connected to a resistor. The total resistance in the circuit is 10 ohms. If the longitudinal magnetic induction in the iron changes from 1 weber $m^{-2}$, in the direction to 1 Weber $m^{-2}$ in the opposite direction, how much charge flows through the circuit
Question 823 :
<br>The magnitude of the induced electric field in the orbit at any instant of time during the time interval of themagnetic field change, is
Question 824 :
A train is moving from south to north with a velocity of $90$ km/h. The vertical component of earth's magnetic induction is $0.4\times { 10 }^{ -4 }\quad Wb/{ m }^{ 2 }.$ If the distance between the two rails is $1 m,$ what is the induced e.m.f. in its axle?<br/>
Question 825 :
A Rowland ring of mean radius $15cm$ has $3500$ turns of wire wound on a ferromagnetic core of relative permeability $800$. What is the magnetic field $B$ in the core for a magnetising current of $1.2A$ ?
Question 826 :
A flat circular coil of $n$ turns, area $A$ and resistance $R$ is placed in a uniform magnetic field $B$. The plane of coil is initially perpendicular to $B$. When the coil is rotated through an angle of ${180}^{o}$ about one of its diameter, a charge ${Q}_{1}$ flows through the coil. When the same coil after being brought to its initial position, is rotated through an angle of ${360}^{o}$ about the same axis a charge ${Q}_{2}$ flows through it. Then ${Q}_{2}/{Q}_{1}$
Question 827 :
A coil of 100 turns and 5 square centimeter is placed in a magnetic field B = 0.2 T. The normal to the plane of the coil makes an angle of 60 with the direction of the magnetic field. The magnetic flux linked with the coil is :
Question 828 :
A coil is placed in transversemagnet field of $0.02T$. If this coil starts shrinking at a rate of $1mm/sec$, while its radius remains $4cm$, then what is the value of induced $emf$?
Question 829 :
A generator with a circular coil of $100$ turns of area $2\times { 10 }^{ -2 }{ m }^{ 2 }$ is immersed in a $0.01T$ magnetic field and rotated at a frequency of $50Hz$. The maximum emf which is produced during a cycle is
Question 830 :
Assertion: An induced e.m.f. appears in any coil in which the current is changing
Reason: Self-induction phenomenon obeys Faraday's law<br/>of induction.
Question 831 :
A solenoid has $2000$turns wound over a length of $0.3\ m$. Its cross-sectional area is $1.2\times 10^{-3} m^2$. Around its central section a coil of $300$turns is wound. If an initial current of $2\ A$flowing in the solenoid is reversed in $0.25\ s$, the emf induced in the coil will be<br>
Question 832 :
A ring of resistance $10 \Omega $ , radius $10cm$ and $100$ turns is rotated $100$ revolutions per second about a fixed axis which is perpendicular to a uniform magnetic field of induction $ 10 m T $ . The amplitude of the current in the loop will be nearly (Take $ \pi^2 = 10 $)
Question 833 :
Charge Q is uniformly distributed on a thin insulating ring of mass m which is initially at rest. To what angular velocity will the ring be accelerated when a magnetic field B, perpendicular to the plane of the ring, is switched on?<br><br>
Question 834 :
A flat coil of radius 5 cm with 50 turns has a resistance of 0.16 $\Omega$ and is placed in a magnetic field oriented normal to the plane of the coil. The magnetic field varies at a constant rate in time. By switching the magnetic field on at t = 0 s, the rate of heat dissipated in the coil is found to be  $0.49 Js^{-1}$. Then choose the correct options from the following.
Question 836 :
An electric bulb has a rated power of $50 W$ at $100 V$. If it is used on an AC source $200 V$, $50 Hz$, a choke has to be used in series with it. This choke should have an inductance of<br/>
Question 838 :
A thin circular ring of area $A$ is held perpendicular to a uniform magnetic field of induction $B$. A small cut is made in the ring and a galvanometer is connected across the ends such that the total resistance of the circuit is $R$. When the ring suddenly squeezed to zero area, the charge flowing through the galvanometer is :<br/>
Question 839 :
A square of side L meters lies in the x-y plane in a region where the magnetic field is given by $\bar{B}= B_0(2\hat{i}+3\hat{j}+4\hat{k})T$,where $B_0$ is constant. The magnitude of flux passing through the square is:
Question 840 :
Magnetic flux linked with a stationary loop resistance $R$ varies with respect to time during the time period $T$ as follows:<br>$\phi=at(T-t)$<br>The amount of heat generated in the loop during that time (inductance of the coil is negligible) is
Question 841 :
Self inductance $L$ of long solenoid is being proportional to the number of turns $N$ as-<br>
Question 842 :
A flexible wire loop in the shape of a circle has a radius that grows linearly with time. There is a magnetic field perpendicular to the plane of the loop that has a magnitude inversely proportional to the distance from the center of the loop, $B(r)\propto \cfrac{1}{r}$. How does the emf vary with time?
Question 843 :
A circular coil of radius $10\ cm, 500$ turns and resistance $2\Omega$ is placed with its plane perpendicular to the horizontal component of the earth's magnetic field. If is rotated about its vertical diameter through $180^{\circ}m$ in $0.25\ s$. The current induced in the coil is<br>(Horizontal component of the earth's magnetic field at that place is $3.0\times 10^{-5}T)$.
Question 844 :
Two identical coaxial circular loops carry a current I each<br/>circulating in the same direction If the loops approach each other, you will observe that<br/>
Question 845 :
Find the inductance of a solenoid of length $l_0$, made of Cu windings of mass $m$. The winding resistance is equal to $R$. The diameter of solenoid << $l$. $\rho_0$ is resistivity of Cu and $\rho$ is density of the Cu.
Question 846 :
A fan operates at 200 V(dc) consuming 1000 W when running at full speed. Its internal wiring has resistance $1 \omega $. When the fan runs at full speed, its speed become constant. This is because the torque due to magnetic field inside the fan is balanced by the torque due to air resistance on the blades of the fan and torque due to friction between the fixed part and the shaft of the fan. The electrical power going into the fan is spent (i) in the internal resistance as heat, call it $P_1$(ii) in doing work against internal friction and air resistance producing heat, sound, etc. Call it $P_2$. When the coil of fan rotates,an emf is also induced in the coil. This opposes the external emf applied to send the current into the fan. This emf is called back emf, call it e. Answer the following question when the fan is running at full speed.<br><br>The value of power $P_2$ is<br>
Question 848 :
A long solenoid having $200$ turns per cm carries a current of $1.5 amp.$ At the centre of it is placed a coil of $100$ turns of cross-sectional are $3.14\times 10^{-4}m^2$ having its axis parallel to the field produced by the solenoid. When the direction of current in the solenoid is reversed within $0.05 sec,$ the induced e.m.f. in the coil is<br/>
Question 849 :
The magnitude of induced emf on the closed surface of ring will be
