Question 1 : If the charge $+Q$ is now at the centre of a cube of side $2l$, what is the total flux emerging from all the six faces of the closedsurface?

Question 2 : The electric field $0.50 m$ from a small sphere with a positive charge of $7.2\times 10^{5} C$ is

Question 3 : Given a uniform electric field $E=5 \times 10^3\hat i N/C$. Find the flux of this field through a square of side $10cm$ on a side whose plane is parallel to YZ-plane :

Question 4 : Mathematically, electric flux can $\phi$be represented as:<br><br>$\vec E =$ electric field<br>$\hat n=$ surface normal vector<br>$A=$ surface area

Question 5 : An electric charge $q$is placed at the centre of a cube of side $a$ The electric flux throughone of its faces is

Question 6 : Charges Q, 2Q and 4Q are uniformly distributed in three dielectric solid spheres 1,2 and 3 of radii R/2,R and 2R respectively. If magnitudes of the electric fields at point P at a distance R from the centre of sphere 1, 2 and 3 are $E_1$, $E_2$ and $E_3$ respectively, then :<br/>

Question 7 : <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 8 : Three resistors are connected in parallel across a potential difference and a current&#160;$I$&#160;passes through it, the resistance values are such that $R_1 &lt; R_2 &lt;&#160;R_3$,&#160;then the ratio of branch currents in the same order is:

Question 9 : 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 11 : 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 12 : Find the electric field in the copper wire of area of cross section $2\ mm^2$ carrying a current of $1\ A.$ The resistivity of copper is $1.7\times 10^{-8}\Omega m$.<br>

Question 13 : 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 14 : Drift velocity varies with the intensity of electric field as per the relation

Question 15 : 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&#160;<br/>

Question 16 : 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 17 : 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 18 : 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 20 : The resistivity of the conductors is of the order of _______.

Question 21 : If two resistors of resistance 30 $\Omega$ and 40 $\Omega$ are connected in parallel across a battery. The ratio of the potential difference across them is _____.

Question 22 : 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 23 : You are given $5 &#160; m$ length of heating wire, it has resistance of $24 &#160; \Omega$. It is cut into two and connected to $110$ volt line individually. The total power for the two half lengths is:

Question 24 : 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 25 : Two long parallel wires are separated by a distance of $2.50 cm$.The force per unit length that each wire exerts on the other is $4.00\times {10}^{-5}N/m$, and the wires repel each other. The current in one wire is $0.600 A$.&#160;What is the current in the second wire?

Question 26 : 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 27 : 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 28 : Electron moves at right angles to a magnetic field of $1.5\times 10^{-2}$ tesla with speed of $6\times 10^7m/s$. If the specific charge of the electron is $1.7\times 10^{11}C/kg$. The radius of circular path will be<br>

Question 29 : A charged particle moves in a gravity free space where an electric field of strength E and a magnetic field of induction B exist. Which of the following statement is/are correct?<br>

Question 30 : A proton, a deuteron and an $\alpha-particle$ having the same kinetic energy are moving in circular trajectories in a constant magnetic field. If $r_p, r_d$ and $r_{\alpha}$ denote, respectively, the radii of the trajectories of these particles, then<br>

Question 31 : A particle of mass $m$ and charge $q$ moves with a constant velocity $v$ along the positive $x-$ direction. It enters a region containing a uniform magnetic field $B$ directed along the negative $z-$ direction, extending from $x=a$ to $x=b$. The minimum value of $v$ required so that the particle can just enter the region $x &gt; b$ is<br>

Question 32 : A circular coil carrying current 'I' has a radius 'R' and magnetic field at the center is 'B'. At what distance from the center along the axis of the same coil, the magnetic field will be $\dfrac{B}{8}$?

Question 33 : &#160;A &#160;cyclotron accelerates deuterons to $16 MeV$ energy. lf deuterium is replaced by helium what will be the energy of alpha particles?<br/>

Question 34 : 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 35 : A proton is acceleratingon a cyclotron having oscillating frequency of 11 MHz in external magnetic field of 1 T. If the radius of its dees is 55 cm, then its kinetic energy (in MeV) is ($m_p = 1.67 \times 10^{-27} \ kg$, $e = 1.6 \times 10^{-19} \ C$)

Question 36 : A coil carrying current '$I$' has radius '$r$' and number of turns '$n$'. It is rewound so that radius of new coil is '$\dfrac{r}{4}$' and it carries current '$I$'. The ratio of magnetic moment of new coil to that of original coil is

Question 37 : A particle having charge $10$ times that of the electron revolves in a circular path of radius $0.4m$ with an angular speed of one rotation per second. The magnetic induction produced at the centre of the circular path is:

Question 38 : 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 39 : A charged particle moves through a magnetic field perpendicular to its direction, then

Question 40 : A given length of wire can be bent to form a circle or a square of single turn and a current may be established in it. The ratio of magnetic field at the centre of circle to that at the centre of square is :

Question 41 : An alternating electric field, of frequency v, is applied across the dees (radius $=$ R) of a cyclotron that is being used to accelerate protons (mass $=$ m). The operating magnetic field (B) used in the cyclotron and the kinetic energy (K) of the proton beam, produced by it, are given by

Question 42 : In which case will the particle move in a straight line with constant velocity?

Question 43 : 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 $\left(\dfrac{charge \ &#160;on \ &#160;the \ &#160;ion}{mass \ &#160;of \ &#160;the \ &#160;ion}\right)$ will be proportional to

Question 44 : <span class="wysiwyg-font-size-small"><span class="wysiwyg-font-size-small">Whichof the following particles will experience maximum magnetic force (magnitude) when projected with the same velocity perpendicular to a magnetic field?<br>

Question 45 : A magnetic field $4\times 10^{-3}(\hat{k})$T exerts a force $(4\hat{i}+3\hat{j})\times 10^{-10}$N on a particle having a charge $10^{-9}$C and going in the X-Y plane. The velocity of the particle (in m/s) is?

Question 46 : A solenoid of 0.4 m length&#160;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 47 : When a charged particle moves only electric or a magnetic field, its speed is $v$ and acceleration is $a$

Question 48 : 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 49 : <br/>A charged particle with specific charge s moves undeflected through a region of space containing mutually perpendicular and uniform electric and magnetic fields E and B. When E is switched off the particle will move in a circular path of radius<br/><br/><br/>

Question 50 : A cyclotron is operated at an oscillator frequency of $\dfrac{80}{\pi }MHz$ and has a Dee of radius $\:R = 60\ cm$. The magnitude of magnetic field $B$ (in Tesla) to accelerate deuteron is $\dfrac{x}{10}$ Tesla. Find x ? (charge on deuteron $e=1.6\times10^{-19}$ mass of deuteron $=3.24\times 10^{-27}\ Kg)$<br/>

Question 51 : Consider two thin identical conducting wires covered with very thin insulating material. One of the wires is bent into a loop and produces magnetic field $B_1$, at its centre when a current $I$ passes through it. The second wire is bent into a coil with three identical loops adjacent to each other produces magnetic field $B_2$ at the centre of the loops when current $\dfrac{I}{3}$ passes through it. The ratio $B_1 : B_2$ is :

Question 53 : <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 54 : A coil having $n$ turns and resistance $R$ $\Omega$ is&#160;connected with a galvanometer of resistance $4R$ $\Omega$. This combination is moved in time $t$ seconds&#160;from a magnetic flux $ W_{1}$ to $ W_{2}$.&#160;The induced current in the circuit is<br/>

Question 55 : A vertical ring of radius $r$ and resistance $R$ falls vertically. It is in contact with two vertical rails which are joined at the top. The rails are without friction and resistance. There is a horizontal uniform magnetic field of magnitude $B$ perpendicular to the plane of the ring and the rails. When the speed of the ring is $v$, the current in the top horizontal of the rail section is

Question 56 : 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 57 : 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 58 : 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 59 : 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 60 : The uniform magnetic field perpendicular to the plane of a conducting ring of radius $a$ changes at the rate of $\alpha$, then

Question 61 : 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 becomes 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 current flowing into the fan and the value of back emf e is&#160;

Question 62 : An alternating current generator has an internal resistance $R_{g}$ and an internal reactance $X_{g}$. It is used to supply power to a passive load consisting of a resistance $R_{g}$ and a reactance $X_{L}$. For maximum power to be delivered from the generator to the load, the value of $X_{L}$ is equal to

Question 63 : Light with energy flux of 18$\mathrm { w } / \mathrm { cm } ^ { 2 }$ falls on a non reflecting surface of area 20$\mathrm { cm } ^ { 2 }$ at normal incidence the momentum delivered in $30$ minutes ise

Question 64 : An $n$ sided regular polygon is inscribed in a circular region of radius $R$ using a wire of cross sectional radius $r$ and resistivity $\rho$. If the magnetic field in the circular region has a time rate of change given by $B$ then the current in the wire loop at any time is given by

Question 65 : A very small circular loop of radius $a$ is initially (at $t=0$) coplanar and concentric with a much larger fixed circular loop of radius $b$. A constant current $I$ flows in the larger loop. The smaller loop is rotated with a constant angular speed $\omega $ about the common diameter. The emf induced in the smaller loop as a function of time $t$ is:

Question 66 : A plane electromagnetic wave in a non magnetic dielectric medium is &#10;given by $\bar{E} = \bar{E_0} ( 4 \times 10^{-7}x - 50 t)$ with &#10;distance being in meter and time in seconds. The dielectric constant of &#10;the medium is:

Question 68 : 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 69 : 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 70 : 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 71 : The magnitude of induced emf on the closed surface of ring will be

Question 72 : The incident intensity on a horizontal surface at sea level from the sun is about $1 kW m^{-2}$. Assuming that 50 per cent of this intensity is reflected and 50 per cent is absorbed, determine the radiation pressure on this horizontal surface (in pascals).<br/>

Question 73 : A plane e.m wave of frequency $30MHz$ travels in free space along the x-direction. The electric field component of the wave at a particular point of space and time $E=6V/m$ along $y$-direction. Its magnetic field component $B$ at this point would be

Question 74 : Potential difference across plates of a capacitor $6\mu F$&#160;is changing at the rate of $72V{ s }^{ -1 }$. Displacement current at that instant will be&#160;

Question 75 : The electric fields of two plane electromagnetic plane waves in vacuum are given by<br/>$\vec{E_1}=E_0\hat{j}\cos(\omega t-kx)$ and $\vec{E_2}=E_0\hat{k}\cos(\omega t-ky)$<br/>At $t=0$, a particle of charge q is at origin with a velocity $\vec{v}=0.8c\hat{j}$ (c is the speed of light in vaccum). The instantaneous force experienced by the particle is:<br/>

Question 76 : Suppose that the electric field amplitude of an electromagnetic wave propagating along x-direction is ${ E }_{ 0}$ = 120 N ${ C }^{ -1 }$ and that its frequency is $\upsilon$ = 50.0 MHz.

Question 77 : The electric field part of an electromagnetic wave in vacuum is<br/>$E=3.1\cos { \left[ \left( 1.8\dfrac { rad }{ m }&#160; \right) y+\left( 5.4\times { 10 }^{ 8 }\dfrac { rad }{ s }&#160; \right) t \right] \hat { i }&#160; } $ the wavelength of this part of electromagnetic wave is

Question 78 : A parallel beam of light is incident normally on a plane surface absorbing 40 % of the light and reflecting the rest. If the incident beam carries 60 watt of power, the force exerted by it on the surface is:

Question 79 : A $1.5\ kW$ (kilo-watt) laser beam of wavelength $6400 \mathring A$ is used to levitate a thin aluminium disc of same area as the cross section of the beam. The laser light is reflected by the aluminium disk without any absorption. The mass of the disc is close to:<br/>

Question 80 : A free electron is placed in the path of a plane electromagnetic wave. The electron will start moving

Question 81 : A collimated beam of light of flux density $3k Wm^{-2}$ is incident normally on a $100 mm^2$ completely absorbing screen. If P is the pressure exerted on the screen and $\Delta p$ is the momentum transferred to the screen during a 1000 s interval, then<br>

Question 82 : In an electromagnetic wave, the electric and magnetic fields are $100 Vm ^{-1}$and $0.265 Am$ maximum energy flow is

Question 83 : A plane EM wave travelling alone z-direction is described by ${ \overrightarrow { E }&#160;\&#160; =\&#160; { E }_{ 0 } }\sin { (kz\&#160; -\&#160; \omega t)\hat{ i } }$ and ${\vec B\&#160; =\&#160; { B }_{ 0 } }\sin { (kz\&#160; -\&#160; \omega t)\hat{ j } }$.

Question 84 : If $\vec{E}$ and $\vec{B}$ are the electric and magnetic field vectors of electromagnetic waves, then the direction of propagation of the electromagnetic wave is along the direction of<br>

Question 85 : A light of wavelength $6000 A^0$ in air, enters a medium with refractive index 1.5. What will be the wavelength of light in the medium?

Question 86 : Light of intensity$ = 3 W/m^{2}$ is incident on a perfectly absorbing metal surface of area &#160;$1 m^{2}$ making an&#160;angle of $60^0$ with the normal. If the force exerted by the photons on the surface is&#160;$p \times 10^{-9}$ (in Newton), then the value of p is :<br/>

Question 87 : A transformer of efficiency $90$% has turns ratio $1 : 10$. If the voltage across the primary is $220\ V$ and current in the primary is $0.5\ A$, then the current in secondary is

Question 88 : A $750Hz, 20 V$ source is connected to aresistance of $100\Omega$, an inductance of $0.1803H$and a capacitance of $10\mu F$, all in series. Thetime in which the resistance (thermal capacity $=2J/^{0}C$) will get heated by $10^{0}C$ is<br>

Question 89 : An AC source rated 100 V (rms) supplies currentof 10 A (rms) to a circuit. The averagepower delivered by the source

Question 90 : A certain choke coil of negligible resistance draws&#160;a current of 8A, when connected to a supply of&#160;100 volts, at 50Hz. A certain non-inductive&#160;resistance, under the same conditions carries a&#160;current of 10 A. If the two are transferred to a&#160;supply system working at 150 V, at 40 Hz, the&#160;total current they will take if joined in series is<br/>

Question 91 : An alternating current of $1.5mA$ and angular frequency $300\ rad/sec$ flows through a $10K\Omega$ resistor and a $0.50\mu F$ capacitor in series. find the rms voltage across the capacitor and impedance of the circuit?

Question 92 : The power developed in the circuit of a $2500\space \mu F$ capacitor that is connected in series with the coil is:

Question 93 : In an L-R circuit, the voltage is given by $V$ as $283 sin 314t$. The current is found tc be $4 \, sin \left ( 314t-\dfrac {\pi}{4} \right )$Calculate the resistance of the circuit.&#160;

Question 94 : In an oscillating $L-C$ circuit in which $C=4.00\mu F$, the maximum potential across the capacitor during the oscillations is $1.50V$ and the maximum current through the inductor is $50.0mA$.&#160;How much time does the charge on the capacitor take to rise from zero to its maximum value?

Question 96 : Then the energy dissipated in the circuit in $20\space min$ is:

Question 97 : Two coil have a mutual inductance 0.005 H. The current changes in first coil according to equation$I = {I_0}\sin \omega t$ where ${I_0} = 2A$ and $\omega = 100\pi \ rad/\sec $ , where . The maximum value of induced emf in second coil is:

Question 98 : The average power dissipated in a pure inductor of inductance Lwhen an ac current is passing through it, is<br>(Inductance of the coil L and current I)<br>

Question 99 : A RC series circuit of R$=15\Omega$ and $C=10\mu F$ is connected to $20$ volt DC supply for very long time. Then capacitor is disconnected from circuit and connected to inductor of $10$mH. Find amplitude of current.

Question 100 : An $LCR$ circuit contains resistance of $100\Omega$ and a supply of $200\space V$ at $300\space rad/s$ angular frequency. If only capacitance is taken out from the circuit and the rest of the circuit is joined, current lags behind the voltage by $60^{\small\circ}$. If on the other hand, only inductor is taken out, the current leads by $60^{\small\circ{}}$ with the applied voltage. The current flowing in the circuit is

Question 101 : Statement-1 : An emf $\varepsilon=\varepsilon_0 sin \left ( \omega t + \frac{\pi}{6} \right )$ is applied in a circuit and a current $i=i_0 &#160;sin &#160;\left ( \omega t - \frac{\pi}{3} \right )$ flows. Then the average power delivered by the source is zero.<br/>Statement-2 : If &#160; the average &#160;value of &#160;$\varepsilon $&#160; and $ i$&#160;is separately &#160;zero, &#160;then &#160;the &#160;power &#160;consumed &#160;will be &#160;zero.<br/>

Question 102 : An alternating voltage given as $V=100\sqrt { 2 } \sin { 100t } \quad $is applied to a capacitor of $1\mu F$. The current reading of the ammeter will be equal to ______ mA.

Question 103 : An $L-C$ circuit consists of an inductor of $L=0.0900H$ and a capacitor of $C=4\times {10}^{-4}F$. The initial charge on the capacitor is $5.00\mu C$ and the initial current in the inductor is zero. When the current in the inductor has half its maximum value,&#160;what is the energy stored in the inductor?

Question 104 : The self inductance of the motor of an electric fan is $10\ H$. In order to impart maximum power at $50\ Hz$, it should be connected to a capacitance of

Question 105 : In an oscillating $L-C$ circuit in which $C=4.00\mu F$, the maximum potential across the capacitor during the oscillations is $1.50V$ and the maximum current through the inductor is $50.0mA$.&#160;What is the inductance $L$?

Question 106 : The ratio of the secondary to the primary turns in a&#160;transformer is $3 : 2$ and the output power is $P$.&#160;Neglecting all power losses, the input power must&#160;be<br/>

Question 107 : 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 108 : 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 109 : 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 110 : 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 111 : 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 112 : 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.&#160;What is the surface charge density on each plate?<br/>

Question 113 : The displacement current flows in the dielectric of a capacitor when the potential difference across its plate<br/>

Question 114 : 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 115 : 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 116 : In 1909, Robert Millikan was the first to find the charge of an electron&#10; in his now-famous oil-drop experiment. In that experiment, tiny oil &#10;drops were sprayed into a uniform electric field between a horizontal &#10;pair of oppositely charged plates.The drops were observed with a &#10;magnifying eyepiece, and the electric field was adjusted so that the &#10;upward force on some negatively charged oil drops was just sufficient to&#10; balance the downward force of gravity. That is, when suspended, upward &#10;force qE&#160;just equaled mg. Millikan accurately measured the charges on &#10;many oil drops and found the values to be whole number multiples of &#10;$1.6 &#160;\times 10^{-19} C$ the charge of the electron. For this, he won &#10;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 117 : 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 118 : 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 119 : 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 120 : 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 121 : A parallel plate capacitor is charged from a cell and then isolated from it. The separation between the plates is now increased :<br/>

Question 122 : A parallel plate capacitor is charged and then the battery is disconnected, When the plates of the capacitor are brought closer, then<br>

Question 123 : 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 124 : 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 125 : 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 126 : <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 127 : In 1909, Robert Millikan was the first to find the charge of an electron&#10; in his now-famous oil-drop experiment. In that experiment, tiny oil &#10;drops were sprayed into a uniform electric field between a horizontal &#10;pair of oppositely charged plates.The drops were observed with a &#10;magnifying eyepiece, and the electric field was adjusted so that the &#10;upward force on some negatively charged oil drops was just sufficient to&#10; balance the downward force of gravity. That is, when suspended, upward &#10;force qE&#160;just equaled mg. Millikan accurately measured the charges on &#10;many oil drops and found the values to be whole number multiples of &#10;$1.6 &#160;\times 10^{-19} C$ the charge of the electron. For this, he won &#10;the Nobel prize. Extra electrons on this particular oil drop (given the presently known charge of the electron) are :<br/>

Question 128 : <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 129 : 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 130 : 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 131 : 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 132 : A parallel plate&#160;condenser has&#160;two circular&#160;metal plates of radius&#160;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 133 : 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 134 : 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 135 : Three capacitance of capacity $10 \mu F , 5 \mu F $ are connected in parallel. The total capacity will be :

Question 136 : 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 137 : The work done in placing a charge of $8\times &#160;10^{-18} C$ on a condenser of capacity $100\mu F$ is :<br/>

Question 138 : A parallel plate capacitor is charged and then the battery is disconnected, When the plates of the capacitor are brought closer, then<br>

Question 139 : A parallel plate capacitor is charged from a cell and then isolated from it. The separation between the plates is now increased :<br/>

Question 140 : 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 141 : 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 142 : 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 143 : 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 144 : 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 145 : 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 146 : 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 147 : 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.&#160;What is the total energy stored in the capacitor?<br/>

Question 148 : 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 149 : 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 150 : 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 151 : Three capacitors of same capacitance are connected in parallel When they are connected to a cell of $2$ volt, total charge of $1.8 \mu C$&#160;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 152 : 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 154 : <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>