# NEET

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

## Biology

Current Electricity

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Q 1. When 5{tex} \mathrm { V } {/tex} potential difference is applied across a wire of length 0.1{tex} \mathrm { m } {/tex} , the drift speed of electrons is {tex} 2.5 \times 10 ^ { - 4 } \mathrm { ms } ^ { - 1 } {/tex} . If the electron density in the wire is {tex} 8 \times 10 ^ { 28 } \mathrm { m } ^ { - 3 } , {/tex} the resistivity of the material is close to:

A

{tex} 1.6 \times 10 ^ { - 6 } \Omega m {/tex}

{tex} 1.6 \times 10 ^ { - 5 } \Omega m {/tex}

C

{tex} 1.6 \times 10 ^ { - 8 } \Omega m {/tex}

D

{tex} 1.6 \times 10 ^ { - 7 } \Omega m {/tex}

##### Explanation

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Q 2. Variation of current passing through a conductor as the voltage applied across its ends is varied as shown in the adjoining diagram. If the resistance {tex} ( R ) {/tex} is determined at the points {tex} A , B , C {/tex} and {tex} D , {/tex} we will find that

A

{tex} R _ { C } = R _ { D } {/tex}

B

{tex} R _ { B } > R _ { A } {/tex}

C

{tex} R _ { C } > R _ { B } {/tex}

{tex} R _ { A } > R _ { B } {/tex}

##### Explanation

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Q 3. The length of a wire of a potentiometer is {tex} 100 \mathrm { cm } , {/tex} and the e. m.f. of its standard cell is {tex} \mathrm { E } {/tex} volt. It is employed to measure the e.m.f. of a battery whose internal resistance is 0.5{tex} \Omega {/tex} . If the balance point is obtained at {tex} \ell = 30 \mathrm { cm } {/tex} from the positive end, the e.m.f. of the battery is

A

{tex} \frac { 30 E } { 100.5 } {/tex}

B

{tex} \frac { 30 E } { ( 100 - 0.5 ) } {/tex}

C

{tex} \frac { 30 ( E - 0.5 i ) } { 100 } {/tex}

{tex} \frac { 30 E } { 100 } {/tex}

##### Explanation

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Q 4. The masses of the three wires of copper are in the ratio of {tex} 1 : 3 : 5 {/tex} and their lengths are in the ratio of {tex} 5 : 3 : 1 . {/tex} The ratio of their electrical resistance is

A

{tex} 1 : 3 : 5 {/tex}

B

{tex} 5 : 3 : 1 {/tex}

C

{tex} 1 : 25 : 125 {/tex}

{tex} 125 : 15 : 1 {/tex}

##### Explanation

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Q 5. n equal resistors are first connected in series and then connected in parallel. What is the ratio of the maximum to the minimum resistance?

A

{tex} n {/tex}

B

{tex} \frac{1} {n ^ { 2 }} {/tex}

{tex}n^{2}{/tex}

D

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

##### Explanation

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Q 6. A battery is charged at a potential of 15{tex} \mathrm { V } {/tex} for 8 hours when the current flowing is 10{tex} \mathrm { A } {/tex} . The battery on discharge supplies a current of 5{tex} \mathrm { A } {/tex} for 15 hours. The mean terminal voltage during discharge is 14{tex} \mathrm { V } {/tex} . The "watt-hour" efficiency of the battery is

87.5{tex} \% {/tex}

B

82.5{tex} \% {/tex}

C

80{tex} \% {/tex}

D

90{tex} \% {/tex}

##### Explanation

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Q 7. Shown in the figure below is a meter-bridge set up with null deflection in the galvanometer.

The value of the unknown resistor R is

A

13.75{tex} \Omega {/tex}

220{tex} \Omega {/tex}

C

110{tex} \Omega {/tex}

D

55{tex} \Omega {/tex}

##### Explanation

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Q 8. A torch bulb rated as 4.5 W , 1.5 V is connected as shown in fig. The e.m.f of the cell, needed to make the bulb glow at full intensity is

A

4.5 V

B

1.5 V

C

267 V

13.5 V

##### Explanation

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Q 9. In a given network, each resistance has value of {tex} 6 \Omega . {/tex} The point {tex} X {/tex} is connected to point A by a copper wire of negligible resistance and point {tex} Y {/tex} is connected to point {tex} B {/tex} by the same wire. The effective resistance between {tex} X {/tex} and {tex} Y {/tex} will be

A

{tex} 18\Omega {/tex}

B

{tex} 6\Omega {/tex}

C

{tex} 3\Omega {/tex}

{tex} 2\Omega {/tex}

##### Explanation

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Q 10. In a large building, there are 15 bulbs of {tex} 40 \mathrm { W } , 5 {/tex} bulbs of 100 {tex} \mathrm { W } , 5 {/tex} fans of 80{tex} \mathrm { W } {/tex} and 1 heater of 1{tex} \mathrm { kW } {/tex} . The voltage of electric mains is 220{tex} \mathrm { V } {/tex} . The minimum capacity of the main fuse of the building will be:

A

8{tex} \mathrm { A } {/tex}

B

10{tex} \mathrm { A } {/tex}

12{tex} \mathrm { A } {/tex}

D

14{tex} \mathrm { A } {/tex}

##### Explanation

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Q 11. The resistance of the series combination of two resistances is {tex} S {/tex}. When they are joined in parallel the total resistance is {tex} P {/tex} . If {tex} S = n P {/tex} then the minimum possible value of {tex} n {/tex} is

A

2

B

3

4

D

1

##### Explanation

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Q 12. In the given circuit diagram when the current reaches steady state in the circuit, the charge on the capacitor of capacitance C will be:

{tex} C E \frac { r _ { 2 } } { \left( r + r _ { 2 } \right) } {/tex}

B

{tex} C E \frac { r _ { 1 } } { \left( \mathrm { r } _ { 1 } + \mathrm { r } \right) } {/tex}

C

{tex} C E \frac { r _ { 2 } } { \left( r + r _ { 1 } \right) } {/tex}

D

{tex} C E \frac { r _ { 1 } } { \left( r _ { 2 } + r \right) } {/tex}

##### Explanation

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Q 13. Suppose the drift velocity {tex} v _ { d } {/tex} in a material varied with the applied electric field {tex} E {/tex} as {tex} v _ { d } \propto \sqrt { E } . {/tex} Then {tex} V - I {/tex} graph for a wire made of such a material is best given by:

A

B

D

##### Explanation

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Q 14. In a neon gas discharge tube Ne' ions moving through a cross-section of the tube each second to the right is {tex} 2.9 \times {/tex} {tex} 10 ^ { 18 } {/tex} , while {tex} 1.2 \times 10 ^ { 18 } {/tex} electrons move towards left in the same time; the electronic charge being {tex} 1.6 \times 10 ^ { - 19 } \mathrm { C } , {/tex} the net electric current is

A

0.27{tex} \mathrm { A } {/tex} to the right

0.66 A to the right

C

0.66 A to the left

D

zero

##### Explanation

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Q 15. Two rods are joined end to end, as shown. Both have a cross-sectional area of {tex} 0.01 \mathrm { cm } ^ { 2 } . {/tex} Each is 1 meter long. One rod is of copper with a resistivity of {tex} 1.7 \times 10 ^ { - 6 } {/tex} ohm-centimeter, the other is of iron with a resistivity of {tex} 10 ^ { - 5 } {/tex} ohm-centimeter. How much voltage is required to produce a current of 1 ampere in the rods?

0.117{tex} \mathrm { V } {/tex}

B

0.00145{tex} \mathrm { V } {/tex}

C

0.0145{tex} \mathrm { V } {/tex}

D

{tex} 1.7 \times 10 ^ { - 6 } \mathrm { V } {/tex}

##### Explanation

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Q 16. An energy source will supply a constant current into the load if its internal resistance is

A

very large as compared to the load resistance

B

equal to the resistance of the load

C

non-zero but less than the resistance of the load

zero

##### Explanation

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Q 17. The resistance of a wire at room temperature: {tex} 30 ^ { \circ } \mathrm { C } {/tex} is found to be {tex} 10 \Omega . {/tex} Now to increase the resistance by {tex} 10 \% , {/tex} the temperature of the wire must be [ The temperature coefficient of resistance of the material of the wire is {tex} 0.002 \text { per } ^ { \circ } \mathrm { C } {/tex} ]

A

{tex} 36 ^ { \circ } \mathrm { C } {/tex}

{tex} 83 ^ { \circ } \mathrm { C } {/tex}

C

{tex} 63 ^ { \circ } \mathrm { C } {/tex}

D

{tex} 33 ^ { \circ } \mathrm { C } {/tex}

##### Explanation

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Q 18. In the circuit shown in figure, the 5W resistance develops 20.00 cal/s due to the current flowing through it. The heat developed in 2 Ω resistance (in cal/s) is

A

23.8

14.2

C

11.9

D

7.1

##### Explanation

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Q 19. In a Wheatstone's bridge, three resistances {tex} P , Q {/tex} and {tex} R {/tex} connected in the three arms and the fourth arm is formed by two resistances {tex} S _ { 1 } {/tex} and {tex} S _ { 2 } {/tex} connected in parallel. The condition for the bridge to be balanced will be

A

{tex} \frac { P } { Q } = \frac { 2 R } { S _ { 1 } + S _ { 2 } } {/tex}

{tex} \frac { P } { Q } = \frac { R \left( S _ { 1 } + S _ { 2 } \right) } { S _ { 1 } S _ { 2 } } {/tex}

C

{tex} \frac { P } { Q } = \frac { R \left( S _ { 1 } + S _ { 2 } \right) } { 2 S _ { 1 } S _ { 2 } } {/tex}

D

{tex} \frac { P } { Q } = \frac { R } { S _ { 1 } + S _ { 2 } } {/tex}

##### Explanation

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Q 20. A car battery has e.m.f. 12 volt and internal resistance 5 x 10-2 ohm. If it draws 60 amp current, the terminal voltage of the battery will be

15 V

B

3 V

C

5 V

D

9 V

##### Explanation

Here the terminal potential ,
{tex} V=12+IR=12+(60×5×10^{−1}) = 12+3=15V{/tex}

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Q 21. A conducting wire of cross-sectional area 1{tex} \mathrm { cm } ^ { 2 } {/tex} has {tex} 3 \times 10 ^ { 23 } {/tex} charge carriers per {tex} \mathrm { m } ^ { 3 } {/tex} . If wire carries a current of 24 {tex} \mathrm { mA } , {/tex} then drift velocity of carriers is

A

{tex} 5 \times 10 ^ { - 2 } \mathrm { m } / \mathrm { s } {/tex}

B

0.5{tex} \mathrm { m } / \mathrm { s } {/tex}

{tex} 5 \times 10 ^ { - 3 } \mathrm { m } / \mathrm { s } {/tex}

D

{tex} 5 \times 10 ^ { - 6 } \mathrm { m } / \mathrm { s } {/tex}