JEE Main > Current Electricity

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


Q 1.    

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} E {/tex} volt. It is employed to measure the e.m.f. of a battery whose internal resistance is {tex} 0.5 \Omega {/tex}. If the balance point is obtained at {tex} l = 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}

{tex} \frac { 30 E } { 100 } - 0.5 i , {/tex} where {tex} i {/tex} is the current in the potentiometer wire.

D

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

Explanation





Q 2.    

Correct4

Incorrect-1

A {tex}3{/tex} volt battery with negligible internal resistance is connected in a circuit as shown in the figure. The current {tex}I{/tex}, in the circuit will be

A

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

{tex} 1.5 \mathrm {\ A } {/tex}

C

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

D

{tex} ( 1 / 3 ) \mathrm {\ A } {/tex}

Explanation


Q 3.    

Correct4

Incorrect-1

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

A

{tex} 200 \% {/tex}

B

{tex} 100 \% {/tex}

C

{tex} 50 \% {/tex}

{tex} 300 \% {/tex}

Explanation



Q 4.    

Correct4

Incorrect-1

The total current supplied to the circuit by the battery is

A

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

B

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

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

D

{tex} 6 \mathrm {\ A } {/tex}

Explanation



Q 5.    

Correct4

Incorrect-1

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

{tex}4{/tex}

B

{tex} 3 {/tex}

C

{tex}2{/tex}

D

{tex}1{/tex}

Explanation



Q 6.    

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 of the wires are in the ratio of {tex} 4 / 3 {/tex} and {tex} 2 / 3 , {/tex} then the ratio of the currents passing through the wire will be

A

{tex} 3 {/tex}

{tex} 1 / 3 {/tex}

C

{tex} 8 / 9 {/tex}

D

{tex}2{/tex}

Explanation



Q 7.    

Correct4

Incorrect-1

In a metre 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 {tex} 4 X {/tex} against {tex} Y ? {/tex}

{tex} 50 \mathrm {\ cm } {/tex}

B

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

C

{tex} 40 \mathrm {\ cm } {/tex}

D

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

Explanation





Q 8.    

Correct4

Incorrect-1

The thermistors are usually made of

A

metals with low temperature coefficient of resistivity

B

metals with high temperature coefficient of resistivity

metal oxides with high temperature coefficient of resistivity

D

semiconducting materials having low temperature coefficient of resistivity.

Explanation


Q 9.    

Correct4

Incorrect-1

In the circuit, the galvanometer {tex} G {/tex} shows zero deflection. If the batteries {tex} A {/tex} and {tex} B {/tex} have negligible internal resistance, the value of the resistor {tex} R {/tex} will be

A

{tex} 500 \Omega {/tex}

B

{tex} 1000 \Omega {/tex}

C

{tex} 200 \Omega {/tex}

{tex} 100 \Omega {/tex}

Explanation



Q 10.    

Correct4

Incorrect-1

Two sources of equal emf are connected to an external resistance {tex} R {/tex}. The internal resistances of the two sources are {tex} R _ { 1 } {/tex} and {tex} R _ { 2 } \left( R _ { 2 } > R _ { 1 } \right) {/tex}. If the potential difference across the source having intermal resistance {tex} R _ { 2 } {/tex} is zero, then

A

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

B

{tex} R = \frac { R _ { 1 } R _ { 2 } } { R _ { 2 } - R _ { 1 } } {/tex}

C

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

{tex} R = R _ { 2 } - R _ { 1 } {/tex}

Explanation



Q 11.    

Correct4

Incorrect-1

In a potentiometer experiment the balancing with a cell is at length {tex} 240 \mathrm { cm } {/tex}. On shunting the cell with a resistance of {tex} 2 \Omega {/tex}, the balancing length becomes {tex} 120 \mathrm { cm } . {/tex} The internal resistance of the cell is

A

{tex} 4 \Omega {/tex}

{tex} 2 \Omega {/tex}

C

{tex} 1 \Omega {/tex}

D

{tex} 0.5 \Omega {/tex}

Explanation



Q 12.    

Correct4

Incorrect-1

The Kirchhoff's first law {tex} \left( \sum i = 0 \right) {/tex} and second law {tex} \left( \sum i R = \sum E \right) , {/tex} where the symbols have their usual meanings, are respectively based on

conservation of charge, conservation of energy

B

conservation of charge, conservation of momentum

C

conservation of energy, conservation of charge

D

conservation of momentum, conservation of charge.

Explanation


Q 13.    

Correct4

Incorrect-1

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

A

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

B

{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}

D

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

Explanation



Q 14.    

Correct4

Incorrect-1

The current {tex} I {/tex} drawn from the {tex}5 \mathrm {\ volt}{/tex} source will be

A

{tex} 0.17 \mathrm {\ A } {/tex}

B

{tex} 0.33 \mathrm {\ A } {/tex}

{tex} 0.5 \mathrm {\ A } {/tex}

D

{tex} 0.67 \mathrm {\ A } {/tex}

Explanation



Q 15.    

Correct4

Incorrect-1

The resistance of a bulb filament is {tex} 100 \Omega {/tex} at a temperature of {tex} 100 ^ { \circ } \mathrm { C } {/tex}. If its temperature coefficient of resistance be {tex} 0.005 per ^ { \circ } \mathrm { C } , {/tex} its resistance will become {tex} 200 \Omega {/tex} at a temperature of

A

{tex} 200 ^ { \circ } \mathrm { C } {/tex}

B

{tex} 300 ^ { \circ } \mathrm { C } {/tex}

{tex} 400 ^ { \circ } \mathrm { C } {/tex}

D

{tex} 500 ^ { \circ } \mathrm { C } {/tex}

Explanation



Q 16.    

Correct4

Incorrect-1

A material {tex} B {/tex} has twice the specific resistance of {tex} A {/tex}. A circular wire made of {tex} B {/tex} has twice the diameter of a wire made of {tex} A {/tex}. Then for the two wires to have the same resistance, the ratio {tex} l _ { B } / l _ { A } {/tex} of their respective lengths must be

{tex} 2 {/tex}

B

{tex} 1 {/tex}

C

{tex} 1 / 2 {/tex}

D

{tex} 1 / 4 {/tex}

Explanation



Q 17.    

Correct4

Incorrect-1

The resistance of a wire is {tex} 5 {/tex} ohm at {tex} 50 ^ { \circ } \mathrm { C } {/tex} and {tex} 6 {/tex} ohm at {tex} 100 ^ { \circ } \mathrm { C } . {/tex} The resistance of the wire at {tex} 0 ^ { \circ } \mathrm { C } {/tex} will be

A

{tex} 3 {/tex} ohm

B

2 ohm

C

{tex} 1 {/tex} ohm

4 ohm

Explanation



Q 18.    

Correct4

Incorrect-1

A {tex} 5 \mathrm { V } {/tex} battery with internal resistance {tex} 2 \Omega {/tex} and {tex} 2 \mathrm { V } {/tex} battery with internal resistance {tex} 1 \Omega {/tex} are connected to a {tex} 10 \Omega {/tex} resistor as shown in the figure. The current in the {tex} 10 \Omega {/tex} resistor is

A

{tex} 0.27 \mathrm { A } P _ { 1 } {/tex} to {tex} P _ { 2 } {/tex}

B

{tex} 0.27 \mathrm {\ A } P _ { 2 } {/tex} to {tex} P _ { 1 } {/tex}

C

{tex} 0.03 \mathrm {\ A } P _ { 1 } {/tex} to {tex} P _ { 2 } {/tex}

{tex} 0.03 \mathrm {\ AP } _ { 2 } {/tex} to {tex} P _ { 1 } {/tex}

Explanation



Q 19.    

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 resistance {tex} R {/tex} is

A

{tex} 55 \Omega {/tex}

B

{tex} 13.75 \Omega {/tex}

{tex} 220 \Omega {/tex}

D

{tex} 110 \Omega {/tex}

Explanation



Q 20.    

Correct4

Incorrect-1

Current of 4.8 amperes is flowing through a conductor. The number of electrons per second will be

{tex} 3 \times 10 ^ { 19 } {/tex}

B

{tex} 7.68 \times 10 ^ { 21 } {/tex}

C

{tex} 7.68 \times 10 ^ { 20 } {/tex}

D

{tex} 3 \times 10 ^ { 20 } {/tex}

Explanation

Q 21.    

Correct4

Incorrect-1

When the current {tex} i {/tex} is flowing through a conductor, the drift velocity is {tex} v {/tex}. If {tex} 2 i {/tex} current is flowed through the same metal but having double the area of cross-section, then the drift velocity will be

A

{tex} v / 4 {/tex}

B

{tex} v / 2 {/tex}

{tex} { v } {/tex}

D

{tex} 4 v {/tex}

Explanation

Q 22.    

Correct4

Incorrect-1

When current flows through a conductor, then the order of drift velocity of electrons will be

A

{tex} 10 ^ { 10 } \mathrm {\ m } / \mathrm { sec } {/tex}

{tex} 10 ^ { - 2 } \mathrm {\ cm } / \mathrm { sec } {/tex}

C

{tex} 10 ^ { 4 } \mathrm {\ cm } / \mathrm { sec } {/tex}

D

{tex} 10 ^ { - 1 } \mathrm {\ cm } / \mathrm { sec } {/tex}

Explanation

Q 23.    

Correct4

Incorrect-1

Every atom makes one free electron in copper. If 1.1 ampere current is flowing in the wire of copper having 1 mm diameter, then the drift velocity (approx.) will be (Density of copper {tex} = 9 \times 10 ^ { 3 } \mathrm { kg m }^ { - 3 } {/tex} and atomic weight = {tex}63 ){/tex}

A

{tex} 0.3 \mathrm {\ mm } / \mathrm { sec } {/tex}

{tex} 0.1 \mathrm {\ mm } / \mathrm { sec } {/tex}

C

{tex} 0.2 \mathrm {\ mm } / \mathrm { sec } {/tex}

D

{tex} 0.2 \mathrm {\ cm } / \mathrm { sec } {/tex}

Explanation

Q 24.    

Correct4

Incorrect-1

Which one is not the correct statement

A

{tex}1{/tex} volt {tex} \times 1 {/tex} coulomb {tex} = 1 {/tex} joule

B

{tex}1{/tex} volt {tex} \times 1 {/tex} ampere {tex} = 1 {/tex} joule/ second

{tex}1{/tex} volt {tex} \times 1 {/tex} watt {tex} = 1 { H.P. } {/tex}

D

Watt-hour can be expressed in {tex}eV{/tex}

Explanation

Q 25.    

Correct4

Incorrect-1

If a {tex} 0.1 \% {/tex} increase in length due to stretching, the percentage increase in its resistance will be

{tex} 0.2 \% {/tex}

B

{tex} 2 \% {/tex}

C

{tex} 1 \% {/tex}

D

{tex} 0.1 \% {/tex}

Explanation