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Section A, , //X, , •, , Write the answer of the following questions. [Each carries 2 Marks], , 1., , Define network, junction (branch point), loop., , 2., , Write necessary facts to understand Kirchhoff’s laws., , 3., , Write and explain Kirchhoff’s first law (Junction law)., , 4., , Write and explain Kirchhoff’s second law (Loop rule)., , [18], , 3.2), A battery of emf 10 V and internal resistance 3 W is connected to a resistor. If the current in the, 5., circuit is 0.5 A, what is the resistance of the resistor ? What is the terminal voltage of the battery, when the circuit is closed ?, 3B), If, the combination is connected to a battery of emf 12 V and negligible internal resistance, obtain, 6., the potential drop across each resistor., 3.4), (a) Three resistors 2 W, 4 W and 5 W are combined in parallel. What is the total resistance of the, 7., combination ?, , SIR, , (b) If the combination is connected to a battery of emf 20 V and negligible internal resistance,, determine the current through each resistor, and the total current drawn from the battery., 8. ) A negligibly small current is passed through a wire of length 15 m and uniform cross-section 6.0, ´ 10–7 m2, and its resistance is measured to be 5.0 W. What is the resistivity of the material at the, temperature of the experiment ?, , AZ, AZ, , 3.12), In a potentiometer arrangement, a cell of emf 1.25 V gives a balance point at 35.0 cm length of the, 9., wire. If the cell is replaced by another cell and the balance point shifts to 63.0 cm, what is the emf, of the second cell ?, Section B, , //X, , •, , Write the answer of the following questions. [Each carries 3 Marks], , 10., 11., , Explain drift of electron and drift velocity. Derive equation of current in term of cross-section of, conductor., Derive relation between drift velocity and current density., , 12., , Obtain the equation of resistivity of metal., , 13., , Why resistivity of metal decreases with increase in temperature or conductivity decrease with, increase in temperature., , 14., , Explain mobility of conductor and derive equation of mobility., , 15., , What is called series connection of cell ? Derive equation of equivalent emf of two cell with emf e1, and e2 connected in series., , 16., , What is Wheatstone bridge ? Explain its principle., , 17., , Explain how value of unknown resistor can be obtained by using meter bridge., R, , S, B, G, , A, , l1, , D, , 100 – l1, , C, , Meter Scale, , K1, , 18., , What is potentiometer ? Explain principle of potentiometer., , 19., , Explain comparison of emf of two cell by using potentiometer with necessary diagram., , [78]

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20., , Explain method to measure internal resistance of cell by using potentiometer., , 3.1) Estimate the average drift speed of conduction electrons in a copper wire of cross-sectional area, 21., 1.0 ´ 10–7 m2 carrying a current of 1.5 A. Assume that each copper atom contributes roughly, one conduction electron. The density of copper is 9.0 ´ 103 kg/m3 and its atomic mass is 63.5 u., (b) Compare the drift speed obtained above with, (i) thermal speeds of copper atoms at, ordinary temperatures, (ii) speed of propagation of electric field along the conductor which, causes the drift motion., 3.2) (a) In Example 3.1, the electron drift speed is estimated to be only a few mm s–1 for currents in, 22., the range of a few amperes ? How then is current established almost the instant a circuit is, closed ?, (b) The electron drift arises due to the force experienced by electrons in the electric field inside, the conductor. But force should cause acceleration. Why then do the electrons acquire a, steady average drift speed ?, (c) If the electron drift speed is so small, and the electron’s charge is small, how can we still, obtain large amounts of current in a conductor ?, (d) When electrons drift in a metal from lower to higher potential, does it mean that all the ‘free’, electrons of the metal are moving in the same direction ?, (e) Are the paths of electrons straight lines between successive collisions (with the positive ions, of the metal) in the (i) absence of electric field, (ii) presence of electric field ?, , SIR, , 3.5) A network of resistors is connected to a 16 V battery with internal resistance of 1 W, as shown in, 23., figure. (a) Compute the equivalent resistance of the network. (b) Obtain the current in each, resistor. (c) Obtain the voltage drops VAB, VBC and VCD., 4, , 12, B 1, , C, , D, , 4, , AZ, AZ, , A, , 6, , 16V, , 1, , 3.6) A battery of 10 V and negligible internal resistance is connected across the diagonally opposite, 24., corners of a cubical network consisting of 12 resistors each of resistance 1 W (figure). Determine, the equivalent resistance of the network and the current along each edge of the cube., D', , I, 2, A', , 1, , 1, 1, , B', 1, 1, , I, , I, I, , C, , 1, I, B 2 E 10V, , I, 3I I, , C', I, , 1, , I, 2, D, I, 2, , 1, I, A, , 1, , I/2, , I, 2 1, , 1, , 3I, , I, , 1, , 25. ) Determine the current in each branch of the network shown in figure., B, 4W, , 2W, , I2, A, , I1 10V I1, 1W, , I3, I2 + I3, C, , 5V

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) Determine the current in each branch of the network shown in figure., B, 4W, , 2W, , I2, A, , I2 + I3, C, , I1 10V I1, 1W, I1 – I2, 4W, , I3, , 5V, , I, I2 + I3 – I1 2W 3, , D, 3.10) A resistance of RW draws current from a potentiometer. The potentiometer has a total resistance, 26., R0 W as in figure. A voltage V is supplied to the potentiometer. Derive an expression for the voltage, across R when the sliding contact is in the middle of the potentiometer. (All India - 2014), , V, , R0, , R, , C, , B, , SIR, , A, , 27. ) The storage battery of a car has an emf of 12 V. If the internal resistance of the battery is 0.4, W, what is the maximum current that can be drawn from the battery ?, , 3.3) (a) Three resistors 1 W, 2 W and 3 W are combined in series. What is the total resistance of the, 28., combination ?, , AZ, AZ, , (b) If the combination is connected to a battery of emf 12 V and negligible internal resistance,, obtain the potential drop across each resistor., , 29.5) At room temperature (27.0 °C) the resistance of a heating element is 100 W. What is the, temperature of the element if the resistance is found to be 117 W, given that the temperature, coefficient of the material of the resistor is 1.70 ´ 10–4 °C–1 ., 30. ) A silver wire has a resistance of 2.1 W at 27.5 °C and a resistance of 2.7 W at 100 °C. Determine the, temperature coefficient of resistivity of silver., 31. ) A heating element using nichrome connected to a 230 V supply draws an initial current of 3.2 A, which settles after a few seconds to a steady value of 2.8 A. What is the steady temperature of the, heating element if the room temperature is 27.0 °C ? Temperature coefficient of resistance of, nichrome averaged over the temperature range involved is 1.70 ´ 10–4 °C–1., 32. 1) A storage battery of emf 8.0 V and internal resistance 0.5 W is being charged by a 120 V dc supply, using a series resistor of 15.5 W. What is the terminal voltage of the battery during charging ? What, is the purpose of having a series resistor in the charging circuit ?, , 3.13) The number density of free electrons in a copper conductor estimated in Example 3.1 is 8.5 ´ 1028, 33., m–3. How long does an electron take to drift from one end of a wire 3.0 m long to its other end, ? The area of cross-section of the wire is 2.0 ´ 10–6 m2 and it is carrying a current of 3.0 A., 34. 4) The earth’s surface has a negative surface charge density of 10–9 C m–2. The potential difference, of 400 kV between the top of the atmosphere and the surface results (due to the low conductivity, of the lower atmosphere) in a current of only 1800 A over the entire globe. If there were no, mechanism of sustaining atmospheric electric field, how much time (roughly) would be required, to neutralise the earth’s surface ? (This never happens in practice because there is a mechanism, to replenish electric charges, namely the continual thunderstorms and lightning in different parts, of the globe). (Radius of earth = 6.37 ´ 106 m.), , 3.22) Figure shows a potentiometer with a cell of 2.0 V and internal resistance 0.40 W maintaining a, 35., potential drop across the resistor wire AB. A standard cell which maintains a constant emf of 1.02 V, (for very moderate currents upto a few mA) gives a balance point at 67.3 cm length of the wire. To, ensure very low currents drawn from the standard cell, a very high resistance of 600 kW is put in series, with it, which is shorted close to the balance point. The standard cell is then replaced by a cell of, unknown emf e and the balance point found similarly, turns out to be at 82.3 cm length of the wire.

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(for very moderate currents upto a few mA) gives a balance point at 67.3 cm length of the wire. To, ensure very low currents drawn from the standard cell, a very high resistance of 600 kW is put in series, with it, which is shorted close to the balance point. The standard cell is then replaced by a cell of, unknown emf e and the balance point found similarly, turns out to be at 82.3 cm length of the wire., 2V 0.4W, A, , B, , G, 600 kW, , (a) What is the value e ?, (b) What purpose does the high resistance of 600 kW have ?, (c) Is the balance point affected by this high resistance ?, (d) Would the method work in the above situation if the driver cell of the potentiometer had an, emf of 1.0V instead of 2.0V ?, (e) Would the circuit work well for determining an extremely small emf, say of the order of a few, mV (such as the typical emf of a thermocouple) ? If not, how will you modify the circuit ?, (f) Can we use above circuit to measure very small emf of the order of mV. (For example, emf, obtained in thermocouple) ? If not, then what change would you make ?, Section C, , //X, , Write the answer of the following questions. [Each carries 4 Marks], , 36., , Write limitations of Ohm’s law., , 37., , Explain electrical energy and power., , 38., , For reduce in Ohmic loss transmission of electric power at very far distance of electric power is, done at very high voltage ?, , SIR, , •, , [36], , Explain series connection of resistors. Derive equation of equivalent resistance (RS)., , 40., , Write difference between Series and Parallel connection of resistors., Explain cell, emf and internal resistance. Derive relation between potential difference emf and, internal resistance., What is parallel connection of cell ? Obtain equation of equivalent emf of two cell connected in, parallel., , 41., 42., , AZ, AZ, , 39., , 43. ) Determine the current in each branch of the network shown in figure., B, 10, , 5, , A, , C, , 5, 5, , 10, , 10, , 10 V, , 3.10) (a) In a meter bridge as shown in figure, the balance point is found to be at 39.5 cm from the, 44., end A, when the Y resistor is of 12.5 W. Determine the resistance of X. Why are the connections, between resistors in a Wheatstone or meter bridge made of thick copper strips ?, (b) Determine the balance point of the bridge above if X and Y are interchanged., (c) What happens if the galvanometer and cell are interchanged at the balance point of the, bridge ? Would the galvanometer show any current ?, R, , S, B, G, , A, , l1, , D, , 100 – l1, , C

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(c) What happens if the galvanometer and cell are interchanged at the balance point of the, bridge ? Would the galvanometer show any current ?, R, , S, B, G, D, , 100 – l1, , C, , Meter Scale, , SIR, , K1, , AZ, AZ, , A, , l1

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//X, , •, , Section A, Write the answer of the following questions. [Each carries 2 Marks], , 1., , 2., , 3., , Welcome To Future - Quantum Paper, , [18]

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4., , Welcome To Future - Quantum Paper

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Welcome To Future - Quantum Paper

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5., , 6., , Welcome To Future - Quantum Paper

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7., , Welcome To Future - Quantum Paper

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8., , 9., , //X, , •, , Section B, Write the answer of the following questions. [Each carries 3 Marks], , 10., , Welcome To Future - Quantum Paper, , [78]

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11., , Welcome To Future - Quantum Paper

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Welcome To Future - Quantum Paper

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12., , Welcome To Future - Quantum Paper

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13., , 14., , Welcome To Future - Quantum Paper

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15., , Welcome To Future - Quantum Paper

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16., , Welcome To Future - Quantum Paper

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17., , Welcome To Future - Quantum Paper

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18., , Welcome To Future - Quantum Paper

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19., , Welcome To Future - Quantum Paper

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20., , Welcome To Future - Quantum Paper

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21., , Welcome To Future - Quantum Paper

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22., , Welcome To Future - Quantum Paper

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23., , Welcome To Future - Quantum Paper

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24., , Welcome To Future - Quantum Paper

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Welcome To Future - Quantum Paper

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25., , Welcome To Future - Quantum Paper

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26., , Welcome To Future - Quantum Paper

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27., , Welcome To Future - Quantum Paper

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28., , 29., , Welcome To Future - Quantum Paper

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30., , 31., , Welcome To Future - Quantum Paper

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32., , 33., , Welcome To Future - Quantum Paper

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34., , 35., , Welcome To Future - Quantum Paper

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Welcome To Future - Quantum Paper

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//X, , •, , Section C, Write the answer of the following questions. [Each carries 4 Marks], , 36., , Welcome To Future - Quantum Paper, , [36]

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37., , Welcome To Future - Quantum Paper

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38., , 39., , Welcome To Future - Quantum Paper

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Welcome To Future - Quantum Paper

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40., , Welcome To Future - Quantum Paper

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41., , Welcome To Future - Quantum Paper

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Welcome To Future - Quantum Paper

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42., , Welcome To Future - Quantum Paper

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Welcome To Future - Quantum Paper

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43., , Welcome To Future - Quantum Paper

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Welcome To Future - Quantum Paper

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44., , Welcome To Future - Quantum Paper

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Welcome To Future - Quantum Paper