# NEET > Current Electricity

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

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Q 1.

Correct4

Incorrect-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

Q 2.

Correct4

Incorrect-1

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

Q 3.

Correct4

Incorrect-1

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

Q 4.

Correct4

Incorrect-1

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

Q 5.

Correct4

Incorrect-1

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

n

B

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

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

D

{tex}1 / n {/tex}

##### Explanation

Q 6.

Correct4

Incorrect-1

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

Q 7.

Correct4

Incorrect-1

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

Q 8.

Correct4

Incorrect-1

In the equation {tex} \mathrm { AB } = \mathrm { C } , \mathrm { A } {/tex} is the current density, {tex} \mathrm { C } {/tex} is the electric field, Then {tex} \mathrm { B } {/tex} is

resistivity

B

conductivity

C

potential difference

D

resistance

##### Explanation

Q 9.

Correct4

Incorrect-1

The Kirchhoff's first law {tex} ( \Sigma i = 0 ) {/tex} and second law {tex} ( \Sigma i R = \Sigma E ) {/tex} . are respectively based on

A

conservation of charge, conservation of momentum

B

conservation of energy, conservation of charge

C

conservation of momentum, conservation of charge

conservation of charge, conservation of energy

##### Explanation

Q 10.

Correct4

Incorrect-1

You are given a resistance coil and a battery. In which of the following cases the largest amount of heat generated?

A

When the coil is connected to the battery directly

B

When the coil is divided into two equal parts and both the parts are connected to the battery in parallel

When the coil is divided into four equal parts and all the four parts are connected to the battery in parallel

D

When only half the coil is connected to the battery

##### Explanation

Q 11.

Correct4

Incorrect-1

The resistance of the coil of an ammeter is {tex} R {/tex} . The shunt required to increase its range {tex} n {/tex} -fold should have a resistance

A

{tex} \frac { \mathrm { R } } { \mathrm { n } } {/tex}

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

C

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

D

{tex} \mathrm { nR } {/tex}

##### Explanation

Q 12.

Correct4

Incorrect-1

On increasing the temperature of a conductor, its resistance increases because the

A

relaxation time increases

B

mass of electron increases

C

electron density decreases

relaxation time decreases

##### Explanation

Q 13.

Correct4

Incorrect-1

An electric current is passed through a circuit containing two wires of the same material, connected in parallel. If the lengths and radii are in the ratio of {tex} \frac { 4 } { 3 } {/tex} and {tex} \frac { 2 } { 3 } , {/tex} then the ratio of the current passing through the wires will be

A

89

{tex}1 / 3 {/tex}

C

3

D

2

##### Explanation

Q 14.

Correct4

Incorrect-1

In a meter bridge experiment null point is obtained at {tex} 20 \mathrm { cm } , {/tex} from one end of the wire when resistance {tex} X {/tex} is balanced against another resistance {tex} Y . {/tex} If {tex} X < Y {/tex} , then where will be the new position of the null point from the same end, if one decides to balance a resistance of 4{tex} X {/tex} against {tex} Y {/tex}

A

40cm

B

80{tex} \mathrm { cm } {/tex}

50cm

D

70{tex} \mathrm { cm } {/tex}

##### Explanation

Q 15.

Correct4

Incorrect-1

In the circuit shown, the current through 8 ohm is same before and after connecting E. The value of {tex} E {/tex} is

A

12{tex} \mathrm { V } {/tex}

B

6{tex} \mathrm { V } {/tex}

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

D

2{tex} \mathrm { V } {/tex}

##### Explanation

Q 16.

Correct4

Incorrect-1

Find emf {tex} \mathrm { E } {/tex} of the cell as shown in figure.

A

15{tex} \mathrm { V } {/tex}

B

10{tex} \mathrm { V } {/tex}

C

12{tex} \mathrm { V } {/tex}

5{tex} \mathrm { V } {/tex}

##### Explanation

Q 17.

Correct4

Incorrect-1

A torch bulb rated as {tex} 4.5 \mathrm { W } , 1.5 \mathrm { V } {/tex} is connected as shown in fig. The e.m.f of the cell, needed to make the bulb glow at full intensity is

A

{tex} 4.5 \mathrm { Y } {/tex}

B

1.5{tex} \mathrm { V } {/tex}

C

267{tex} \mathrm { V } {/tex}

13.5{tex} \mathrm { V } {/tex}

##### Explanation

Q 18.

Correct4

Incorrect-1

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

18{tex} \Omega {/tex}

B

6{tex} \Omega {/tex}

C

3{tex} \Omega {/tex}

2{tex} \Omega {/tex}

##### Explanation

Q 19.

Correct4

Incorrect-1

If N, e, t and m are representing electron density, charge, relaxation time and mass of an electron respectively, then the resistance of wire of length l and cross-sectional area A is given by

{tex} \frac { 2 m \ell } { N e ^ { 2 } A \tau } {/tex}

B

{tex} \frac { 2 \mathrm { m } \tau \mathrm { A } } { \mathrm { Ne } ^ { 2 } \ell } {/tex}

C

{tex} \frac { \mathrm { Ne } ^ { 2 } \tau \mathrm { A } } { 2 \mathrm { m } \ell } {/tex}

D

{tex} \frac { \mathrm { Ne } ^ { 2 } \mathrm { A } } { 2 \mathrm { m } \mathrm { r } \ell } {/tex}

##### Explanation

Q 20.

Correct4

Incorrect-1

Cell having an emf {tex} \varepsilon {/tex} and internal resistance {tex} r {/tex} is connected across a variable external resistance {tex} R {/tex} . As the resistance {tex} R {/tex} is increased, the plot of potential difference {tex} V {/tex} across {tex} R {/tex} is given by:

A

B

D

##### Explanation

Q 21.

Correct4

Incorrect-1

If voltage across a bulb rated {tex} 220 \mathrm { Volt } - 100 {/tex} Watt drops by 2.5{tex} \% {/tex} of its rated value, the percentage of the rated value by which the power would decrease is:

A

20{tex} \% {/tex}

B

2.5{tex} \% {/tex}

5{tex} \% {/tex}

D

10{tex} \% {/tex}

##### Explanation

Q 22.

Correct4

Incorrect-1

If specific resistance of a potentiometer wire is {tex}10^{–7}{/tex} Wm, the current flow through it is 0.1 A and the cross-sectional area of wire is {tex}10^{–6} m^{2}{/tex} then potential gradient will be

{tex} 10 ^ { - 2 } \mathrm { vol } / \mathrm { m } {/tex}

B

{tex} 10 ^ { - 4 } \mathrm { vol } / \mathrm { m } {/tex}

C

D

{tex} 10 ^ { - 8 } \mathrm { vol } \mathrm { t } / \mathrm { m } {/tex}

##### Explanation

Q 23.

Correct4

Incorrect-1

Two resistances {tex} R _ { 1 } {/tex} and {tex} R _ { 2 } {/tex} are made of different materials. The temperature coefficient of the material of {tex} R _ { 1 } {/tex} is {tex} \alpha {/tex} and that of material of {tex} R _ { 2 } {/tex} is {tex} - \beta {/tex} . The resistance of the series combination of {tex} R _ { 1 } {/tex} and {tex} R _ { 2 } {/tex} will not change with temperature if {tex} \frac { R _ { 1 } } { R _ { 2 } } {/tex} equal to

A

{tex} \frac { \alpha } { \beta } {/tex}

B

{tex} \frac { a + \beta } { a - \beta } {/tex}

C

{tex} \frac { \alpha ^ { 2 } + \beta ^ { 2 } } { 2 \alpha \beta } {/tex}

{tex} \frac { \beta } { \alpha } {/tex}

##### Explanation

Q 24.

Correct4

Incorrect-1

Five cells each of emf 'E' and internal resistance 'r' send the same amount of current through an external resistance 'R' whether the cells are connected in parallel or in series. Then the ratio {tex}\left(\frac{R}{r}\right){/tex} is

A

2

B

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

C

{tex} \frac { 1 } { 5 } {/tex}

1

##### Explanation

Q 25.

Correct4

Incorrect-1

The length of a given cylindrical wire is increased by 100%. Due to the consequent decrease in diameter the change in the resistance of the wire will be

A

200%

B

100%

C

50%

300%