LEVEL – I

1. By increasing the temperature the resistance of a conductor

(A) increases.

(B) decreases.

(C) remains constant.

(D) initially increases then decreases.

2. A battery of emf V volts, resistance R_{1} & R_{2}, a condenser C and switches S_{1} and S_{2} are connected in a circuit as shown in figure. The capacitor C gets fully charged to V volts when

(A) S1 & S2 are both closed

(B) S1 & S2 are both open

(C) S1 closed and S2 open

(D) S2 closed & S1 open.

3. The equivalent resistance of a circuit between A and B is

(A) 3 Ω

(B) zero.

(C) 6 Ω

(D) 3/2 Ω

4. In the circuit shown in figure, the voltmeter reading would be

(A) 0 volt.

(B) 0.5 volt.

(C) 1 volt.

(D) 2 volt.

5. The V-I graph for a conductor at temperatures T_{1} and T_{2} are as shown in the figure, (T_{2} – T_{1}) is proportional to

(A) cos 2θ

(B) sin 2θ

(C) cot2θ

(D) tan 2θ

6. If a copper wire is stretched to make it 0.1 % longer. The percentage change in its resistance is

(A) 0.2 % increase

(B) 0.2% decrease

(C) 0.1 % increase

(D) 0.1 % decrease

7. In the circuit shown in figure E_{1} = 7V, E_{2} = 7V R_{1} = R_{2} = 1 Ω and R_{3} = 3 Ω respectively. The current through the resistance R_{3} is

(A) 2A

(B) 3.5A

(C) 1.75A

(D) none of these

8. The figure shows in apart of an electric circuit, then the current I is

(A) 1 A

(B) 3A

(C) 2 A

(D) 4 A

9. A cell of e.m.f E and internal resistance r is connected across a resistance r. The potential difference between the terminals of the cell must be

(A) E

(B) E/2

(C) E/4

(D) 3E/2

10. A conductor carries a current of 50mA if the area of cross-section of the conductor is 50 mm^{2} then value of the current density in Am-2 is

(A) 0.5

(B) 1

(C) 10-1

(D) 3/10

### ANSWER:

1. A 2. C 3. D 4. A 5. C 6. A 7. A 8. B 9. B 10. B

LEVEL – I

11. In the adjoining circuit, the battery E_{1} has an E.M.F. of 12 volts and zero internal resistance. While the battery E_{2} has an E.M.F. of 2 volts if the galvanometer G reads zero than the value of the resistance X in ohms is

(A) 10

(B) 100

(C) 14

(D) 200

12. Nine similar resistors of resistance R are connected as shown in the figure. Equivalent resistance between points A and B is

(A) 3R/5

(B) 4R/3

(C) 9R/5

(D) R

13. Referring to the adjoining circuit which of the following is/are true

(A) R = 80 ohms

(B) R = 6 ohms

(C) R = 10 ohms

(D) Potential difference between points A & E is 2V

14. In a gas discharge tube if 3 × 10^{18} electrons are flowing per sec from left to right and 2 × 10^{18}protons are flowing per second from right to left a given cross section the magnitude and direction of current through the cross section

(A) 0.48A, left to right

(B) 0.48 A, right

(C) 0.80A, left to right

(D) 0.80 A, right to left

15. In a portion of some large electrical network, current in certain branches are known. The values of (V_{A} – V_{B}) and (V_{C} – V_{D}) are X and Y respectively. Where x and y are

(A) X = 29 V, Y = 26 V

(B) X = 58V, Y = – 52 V

(C) X = -58 V, Y = -52 V

(D) X = -29 V, Y = -26 V

16. A 50 V battery is connected across a 10 Ω resistor and a current of 4 .76 A flows. The internal resistance of the battery is

(A) 0.5 Ω

(B) 0.1 Ω

(C) 0.2 Ω

(D) 0.3 Ω

17. For the circuit shown which of the following statements is true ?

(A) with S_{1} closed, V_{1} = 1 5 V, V_{2} = 20 V

(B) with S_{3} closed V_{1} = V_{2} = 25 V

(C) with S_{1} & S_{2} closed, V_{1} = V_{2} = 0

(D) with S_{1} and S_{3} closed, V_{1} = 30 V, V_{2} = 20 V

18. In the given circuit ammeter and voltmeter are ideal and battery of 6V has internal resistance 1 Ω . The reading of voltmeter and ammeter is

(A) zero, 4/3 Ω

(B) 4/3 V, zero

(C) 6 A, 0.1 A

(D) 3.6 V, 0.6A

19. The maximum power dissipated by external resistance R by a cell of an external emf E and internal resistance r is E^{2}/4R which is obtained for

(A) R < r

(B) R > r

(C) R = r

(D) any value of R.

20. An electric current of 16 A exists in a metal wire of cross section 10^{-6} m^{2} and length 1 m . Assuming one free electrons per atom. The drift speed of the free electrons in the wire will be

(Density of metal = 5 × 10^{3} kg/m^{3}, atomic weight = 60)

(A) 5 × 10^{-3} m/s

(B) 2 × 10^{-3} m/s

(C) 4 × 10^{-3} m/s

(D) 7.5 × 10^{-3} m/s

### ANSWER:

11. B 12. A 13. B 14. D 15. C 16. A 17. D 18. D 19. C 20. B

LEVEL – I

21. 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

(A) r = R/n

(B) r = nR

(C) r = R

(D) r = 1/R

22. A cell of e.m.f. E and internal resistance r is connected in series with an external resistance nr then the ratio of the terminal potential difference to E.M.F. is

(A) 1/n

(B) 1/n+1

(C) n/n+1

(D) n+1/n

23. To measure a potential difference across a resistor of resistance R Ω a voltmeter of resistance R_{v}is used. To measure the potential with a minimum accuracy of 95 % then

(A) R_{v} = 5R

(B) R_{v} = 15 R

(C) R_{v} = 10 R

(D) R_{v} ≥ 19 R

24. A cell of E.M.F. E and internal resistance r supplies currents for the same time t through external resistance R_{1} and R_{2} respectively. If the heat produced in both cases is the same then the internal resistance is

(A) 1/r = 1/R_{1} + 1/R_{2}

(B) r = (R_{1} + R_{2})/2

(C) r = √(R_{1} R_{2})

(D) r = R_{1} + R_{2}

25. A battery of 10 volt is connected to a resistance of 20 ohm through a variable resistance R, the amount of charge which has passed in the circuit in 4 minutes, if the variable resistance R is increased at the rate of 5 ohm/min.

(A) 120 coulomb

(B) 120 log_{e}2 coulomb

(C) 120/log_{e}2 coulomb

(D) 60/log_{e}2 coulomb

26. ABCD is a square of side ‘a’ metres and is made of wires of resistance x ohms/metre. Similar wires are connected across the diagonals AC & BD. The effective resistance between the corners A & C will be

(A) (2 – √2) ax

(B) 6ax

(C) 3ax

(D) (3 – √2) ax

27. To get maximum current in a resistance of 3 Ω , one can use n rows of m cells (connected in series) connected in parallel. If the total no. of cells is 24 and the internal resistance is 0.5 ohm then

(A) m = 12, n = 2

(B) m = 8, n = 3

(C) m = 2, n = 12

(D) m = 6, n = 4

28. In the circuit below the resistance R has a value that depends on the current. Specifically, R is 20 ohms when I is zero and the increase in resistance in ohms is numerically equal to one half of the current in amperes. What is the value of current I in circuit ?

(A) 8.33 amp

(B) 10 amp

(C) 12.5 amp

(D) 18.5 amp

29. The potential difference between points A & B in a section of a circuit shown is

(A) 5 volts

(B) 1 volts

(C) zero volts

(D) 13 volts

30. Two cells of the same e.m.f. e but different internal resistances r_{1} and r_{2} are connected in series with an external resistance ‘R’. the potential drop across the first cell is found to be zero. The external resistance R is

(A) r_{1} – r_{2}

(B) r_{1} / r_{2}

(C) r_{1} r_{2}

(D) r_{1} + r_{2}

### ANSWER:

21. C 22. C 23. D 24. C 25. B 26. A 27. A 28. B 29. D 30. A