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Explore popular questions from Current Electricity for JEE Main. This collection covers Current Electricity previous year JEE Main questions hand picked by experienced teachers.

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Q 1. If resistance of each wire in the network shown is {tex} r , {/tex} the equivalent resistance between {tex} A {/tex} and {tex} C {/tex} is equal to

A

{tex} r {/tex}

B

{tex} \frac { r } { 2 } {/tex}

{tex} \frac { 2 r } { 3 } {/tex}

D

{tex} \frac { 3 r } { 2 } {/tex}

Explanation

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Q 2. In the circuit shown, the potential difference between points {tex} C {/tex} and {tex} B {/tex} will be

A

{tex} ( 8 / 9 ) \mathrm { V } {/tex}

{tex} ( 4 / 3 ) \mathrm { V } {/tex}

C

{tex} ( 2 / 3 ) \mathrm { V } {/tex}

D

4{tex} \mathrm { V } {/tex}

Explanation

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Q 3. The current through 2{tex} \Omega {/tex} resistor is

Zero

B

1{tex} \mathrm { A } {/tex}

C

2{tex} \mathrm { A } {/tex}

D

4{tex} \mathrm { A } {/tex}

Explanation

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Q 4. The equivalent resistance between points {tex} A {/tex} and {tex} B {/tex} in the circuit shown is

A

4{tex} \Omega {/tex}

B

6{tex} \Omega {/tex}

10{tex} \Omega {/tex}

D

8{tex} \Omega {/tex}

Explanation

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Q 5. In the circuit shown in Fig. 14.11 , the reading of voltmeter will be

A

0.8{tex} \mathrm { V } {/tex}

1.33{tex} \mathrm { V } {/tex}

C

1.6{tex} \mathrm { V } {/tex}

D

2.00{tex} \mathrm { V } {/tex}

Explanation

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Q 6. A battery of internal resistance 4{tex} \Omega {/tex} is connected to the network of resistance as shown. In order to give the maximum power to the network, the value of {tex} R {/tex} should be

A

{tex} \frac { 4 } { 9 } \Omega {/tex}

B

{tex} \frac { 8 } { 9 } \Omega {/tex}

2{tex} \Omega {/tex}

D

18{tex} \Omega {/tex}

Explanation

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Q 7. A cell of emf {tex} E {/tex} is connected across a resistance {tex} R {/tex} . The potential difference between the terminals of the cell is found to be {tex} V . {/tex} The internal resistance of the cell must be

A

{tex} \frac { 2 ( E - V ) V } { R } {/tex}

B

{tex} \frac { 2 ( E - V ) R } { E } {/tex}

{tex} \frac { ( E - V ) R } { V } {/tex}

D

{tex} ( E - V ) R {/tex}

Explanation

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Q 8. The equivalent resistance of the network shown in Fig. 14.13 between the base terminals is

A

3{tex} \Omega {/tex}

B

3{tex} \frac { 1 } { 2 } \Omega {/tex}

2{tex} \frac { 2 } { 3 } \Omega {/tex}

D

2{tex} \Omega {/tex}

Explanation

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Q 9. {tex} n {/tex} identical cells, each of emf {tex} \varepsilon {/tex} and internal resistance {tex} r , {/tex} are joined in series to form a closed circuit as shown. The potential difference across any one cell is

Zero

B

{tex} E {/tex}

C

{tex} \frac { \mathcal { E } } { n } {/tex}

D

{tex} \frac { n - 1 } { n } \varepsilon {/tex}

Explanation

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Q 10. In the given circuit, it is observed that the current {tex} I {/tex} is independent of the value of the resistance {tex} R _ { 6 } . {/tex} Then the resistance value must satisfy

A

{tex} R _ { 1 } R _ { 2 } R _ { 5 } = R _ { 3 } R _ { 4 } R _ { 6 } {/tex}

B

{tex} \frac { 1 } { R _ { 5 } } + \frac { 1 } { R _ { 6 } } = \frac { 1 } { \left( R _ { 1 } + R _ { 2 } \right) } + \frac { 1 } { \left( R _ { 3 } + R _ { 4 } \right) } {/tex}

{tex} R _ { 1 } R _ { 4 } = R _ { 2 } R _ { 3 } {/tex}

D

{tex} R _ { 1 } R _ { 3 } = R _ { 2 } R _ { 4 } = R _ { 5 } R _ { 6 } {/tex}

Explanation

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Q 11. A set of {tex} n {/tex} identical resistors, each of resistance {tex} R \Omega {/tex} , when connected in series, has an effective resistance of {tex} x {/tex} ohm. When the resistors are connected in parallel, the effective resistance is {tex} y {/tex} ohm. What is the relation between {tex} R , x , {/tex} and {tex} y ? {/tex}

A

{tex} R = \frac { x y } { ( x + y ) } {/tex}

B

{tex} R = ( y - x ) {/tex}

{tex} R = \sqrt { x y } {/tex}

D

{tex} R = ( x + y ) {/tex}

Explanation

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Q 12. A wire with resistance 12{tex} \Omega {/tex} is bent in the form of a circle. The effective resistance between the two points on any diameter of the circle is

A

12{tex} \Omega {/tex}

B

24{tex} \Omega {/tex}

C

6{tex} \Omega {/tex}

3{tex} \Omega {/tex}

Explanation

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Q 13. A wire {tex} l = 8 \mathrm { m } {/tex} long of uniform cross-sectional area {tex} A = 8 \mathrm { mm } ^ { 2 } {/tex} has a conductance of {tex} G = 2.45 \Omega ^ { - 1 } . {/tex} The resistivity of material of the wire will be

A

{tex} 2.1 \times 10 ^ { - 7 } \Omega \mathrm { m } {/tex}

B

{tex} 3.1 \times 10 ^ { - 7 } \Omega \mathrm { m } {/tex}

{tex} 4.1 \times 10 ^ { - 7 } \Omega \mathrm { m } {/tex}

D

{tex} 5.1 \times 10 ^ { - 7 } \Omega \mathrm { m } {/tex}

Explanation

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Q 14. The potentiometer wire {tex} A B {/tex} is 600{tex} \mathrm { cm } {/tex} long. At what distance from {tex} A {/tex} should the jockey {tex} J {/tex} touch the wire to get zero deflection in the galvanometer?

320{tex} \mathrm { cm } {/tex}

B

120{tex} \mathrm { cm } {/tex}

C

20{tex} \mathrm { cm } {/tex}

D

450{tex} \mathrm { cm } {/tex}

Explanation

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Q 15. In Fig. 14.20, the steady state current in 2{tex} \Omega {/tex} resistance is

A

1.5 {tex}\mathrm A {/tex}

0.9{tex} \mathrm { A } {/tex}

C

0.6{tex} \mathrm { A } {/tex}

D

Zero

Explanation

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Q 16. Kirchoff's second law is based on the law of conservation of

A

Momentum

B

Charge

Energy

D

Sum of mass and energy

Explanation

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Q 17. In the circuit shown in Fig. 14.27, the heat produced in the 5{tex} \Omega {/tex} resistor due to a current flowing in it is 10 calories per second. The heat produced in the 4{tex} \Omega {/tex} resistor is

A

1 {tex} \mathrm { cal } \mathrm { s } ^ { - 1 } {/tex}

2{tex} \mathrm { cal } \mathrm { s } ^ { - 1 } {/tex}

C

3{tex} \mathrm { cal } \mathrm { s } ^ { - 1 } {/tex}

D

4 {tex} \mathrm { cal } \mathrm { s } ^ { - 1 } {/tex}

Explanation

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Q 18. In the circuit shown in Fig. {tex} 14.28 , {/tex} the current through

A

the 3{tex} \Omega {/tex} resistor is 0.50{tex} \mathrm { A } {/tex}

B

the 3{tex} \Omega {/tex} resistor is 0.25{tex} \mathrm { A } {/tex}

C

the 4{tex} \Omega {/tex} resistor is 0.50{tex} \mathrm { A } {/tex}

the 4{tex} \Omega {/tex} resistor is 0.25{tex} \mathrm { A } {/tex}

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Q 19. The meter bridge circuit shown in Fig. is balanced when jockey {tex} J {/tex} divides wire {tex} A B {/tex} in two parts {tex} A J {/tex} and {tex} B J {/tex} in the ratio of {tex} 1 : 2 . {/tex} The unknown resistance {tex} Q {/tex} has value

A

1{tex} \Omega {/tex}

3{tex} \Omega {/tex}

C

4{tex} \Omega {/tex}

D

7{tex} \Omega {/tex}

Explanation

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Q 20. Two identical containers A and B with frictionless pistons contain the same ideal gas at the same temperature and the same volume V. The mass of gas contained in A is and that in B is . The gas in each cylinder is now allowed to expand isothermally to the same final volume 2V. The change in the pressure in A and B are found to be and 1.5 respectively. Then

A

4 = 9

B

2 = 3

3 = 2

D

9 = 4

Explanation

For gas in A,


Putting
We get
Similarly for Gas in B,
From eq. (I) and (II) we get 2 = 3
Hence (C) is the correct.

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Q 21. The alloys constantan and manganin are used to make standard resistance due to they have

A

Low resistivity

B

High resistivity

C

Low temperature coefficient of resistance

Both (b) and (c)

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Q 22. The electric resistance of a certain wire of iron is {tex} R {/tex}. If its length and radius are both doubled, then

A

The resistance will be doubled and the specific resistance will be halved

The resistance will be halved and the specific resistance will remain unchanged

C

The resistance will be halved and the specific resistance will be doubled

D

The resistance and the specific resistance, will both remain unchanged

Explanation

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Q 23. A wire of diameter {tex}0.02{/tex} metre contains {tex} 10 ^ { 28 } {/tex} free electrons per cubic metre. For an electrical current of {tex} 100 A {/tex}, the drift velocity of the free electrons in the wire is nearly

A

{tex} 1 \times 10 ^ { - 19} \mathrm { m } / \mathrm { s } {/tex}

B

{tex} 5 \times 10 ^ { -10 } \mathrm { m } / \mathrm { s } {/tex}

{tex} 2 \times 10^{-4} m / s {/tex}

D

{tex} 8 \times 10^3 \quad m / s {/tex}

Explanation

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Q 24. A current of 2 A flows in a system of conductors as shown. The potential difference {tex} \left( V _ { A } - V _ { B } \right) {/tex} will be

A

{tex} + 2 V {/tex}

{tex} + 1 V {/tex}

C

{tex} - 1 V {/tex}

D

{tex} - 2 V {/tex}

Explanation

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Q 25. Resistances of 6 ohm each are connected in the manner shown in adjoining figure. With the current 0.5 ampere as shown in figure, the potential difference {tex} V _ { P } - V _ { Q } {/tex} is

A

{tex} 3.6 \mathrm { V } {/tex}

B

{tex} 6.0 \mathrm { V } {/tex}

{tex} 3.0 \mathrm { V } {/tex}

D

{tex} 7.2 \mathrm { V } {/tex}

Explanation