JEE Main > Electrostatics

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


Q 1.    

Correct4

Incorrect-1

In the circuit shown, a potential difference of 60{tex} \mathrm { V } {/tex} is applied across {tex} A B {/tex} . The potential difference between the points {tex} M {/tex} and {tex} N {/tex} is

A

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

B

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

C

20{tex} \mathrm { V } {/tex}

30{tex} \mathrm { V } {/tex}

Explanation





Q 2.    

Correct4

Incorrect-1

A positively charged thin metal ring of radius {tex} R {/tex} is fixed in {tex} x - y {/tex} plane with its centre at the origin {tex} O . A {/tex} negatively charged particle {tex} P {/tex} is released from rest at the point {tex} \left( 0,0 , Z _ { 0 } \right) . {/tex} Then the motion of {tex} P {/tex} is

periodic for all values of {tex} Z _ { 0 } {/tex}

B

SHM for all values of {tex} Z _ { 0 } {/tex} satisfying {tex} 0 < Z _ { 0 } < R {/tex}

C

approximately {tex} \mathrm { SHM } , {/tex} provided {tex} Z > R {/tex}

D

cannot be determined.

Explanation

Q 3.    

Correct4

Incorrect-1

Shown in the Fig. 13.32 is a distribution of charges. The flux of electric field due to these charges through the surface is

A

3{tex} q / \varepsilon _ { 0 } {/tex}

B

2{tex} q / \varepsilon _ { 0 } {/tex}

C

{tex} q / \varepsilon _ { 0 } {/tex}

Zero

Explanation

Q 4.    

Correct4

Incorrect-1

Two spherical conductors {tex} A {/tex} and {tex} B {/tex} of radii 1{tex} \mathrm { mm } {/tex} and 2{tex} \mathrm { mm } {/tex} are separated by a distance of 5{tex} \mathrm { cm } {/tex} and are uniformly charged. If the spheres are connected by a conducting wire then in equilibrium condition, the ratio of the magnitude of the electric fields at the surface of spheres {tex} A {/tex} and {tex} B {/tex} is

A

{tex} 1 : 4 {/tex}

B

{tex} 4 : 1 {/tex}

C

{tex} 1 : 2 {/tex}

{tex} 2 : 1 {/tex}

Explanation

Q 5.    

Correct4

Incorrect-1

A point charge {tex} + q {/tex} is fixed at point {tex} B {/tex} . Another point charge {tex} + q {/tex} at {tex} A {/tex} of mass {tex} m {/tex} vertically above {tex} B {/tex} at height {tex} h {/tex} is dropped from rest. Choose the correct statement:

A

It will collide with {tex} B {/tex}

B

It will execute SHM

It will go down only if {tex} \frac { q ^ { 2 } } { 4 \pi \varepsilon _ { 0 } } < m g h ^ { 2 } {/tex}

D

It will go down up to a point and then come up

Explanation

Q 6.    

Correct4

Incorrect-1

The electric field intensity at a point at a distance {tex} 2 \mathrm { m } {/tex} from a charge {tex} q {/tex} is {tex} E . {/tex} The amount of work done in bringing a charge of 2 coulomb from infinity to this point will be

A

2{tex} E \mathbf { J } {/tex}

4{tex} E \mathbf { J } {/tex}

C

{tex} \frac { E } { 2 } \mathbf { J } {/tex}

D

{tex} \frac { E } { 4 } \mathbf { J } {/tex}

Explanation

Q 7.    

Correct4

Incorrect-1

A simple pendulum of length {tex} l {/tex} has a bob of mass {tex} m , {/tex} with a charge {tex} q {/tex} on it. A vertical sheet of charge, with surface charge density {tex} \sigma {/tex} passes through the point of suspension. At equilibrium, the string makes an angle {tex} \theta {/tex} with the vertical, then

{tex} \tan \theta = \frac { \sigma q } { 2 \varepsilon _ { 0 } m g } {/tex}

B

{tex} \tan \theta = \frac { \sigma q } { \varepsilon _ { 0 } m g } {/tex}

C

{tex} \cot \theta = \frac { \sigma q } { 2 \varepsilon _ { 0 } m g } {/tex}

D

{tex} \cot \theta = \frac { \sigma q } { \varepsilon _ { 0 } m g } {/tex}

Explanation





Q 8.    

Correct4

Incorrect-1

A charged particle of mass {tex} m {/tex} and charge {tex} q {/tex} is released from rest in an electric field of constant magnitude {tex} E {/tex} . The kinetic energy of the particle after time {tex} t {/tex} will be

A

{tex} \frac { 2 E ^ { 2 } t ^ { 2 } } { m q } {/tex}

B

{tex} \frac { E q ^ { 2 } m } { 2 t ^ { 2 } } {/tex}

{tex} \frac { E ^ { 2 } q ^ { 2 } t ^ { 2 } } { 2 m } {/tex}

D

{tex} \frac { E q m } { 2 t } {/tex}

Explanation

Q 9.    

Correct4

Incorrect-1

If a positively charged pendulum is oscillating in a uniform field as shown, then its time period as com-pared to that when it was uncharged will

Increase

B

Decrease

C

Not change

D

None of these

Explanation

Q 10.    

Correct4

Incorrect-1

{tex}\ A\ and\ B {/tex} are two concentric metallic hollow spheres. If {tex} A {/tex} is given a charge {tex} q {/tex} while {tex} B {/tex} is earthed as shown in Fig. {tex} 13.33 , {/tex} then

A

charge density of {tex} A {/tex} and {tex} B {/tex} are same.

B

field inside and outside {tex} A {/tex} is zero.

field between {tex} A {/tex} and {tex} B {/tex} is not zero.

D

field inside and outside {tex} B {/tex} is zero.

Explanation

Q 11.    

Correct4

Incorrect-1

A table tennis ball which has been covered with a conducting paint is suspended by a silk thread so that it hangs between two metal plates. One plate is earthed. When the other plate is connected to a high voltage generator, the ball

A

is attracted to the high voltage plate and stays there.

B

hangs without moving.

swings backward and forward hitting each plate in turn.

D

is repelled to the earthed plate and stays there.

Explanation

Q 12.    

Correct4

Incorrect-1

A spring block system undergoes vertical oscillations above a large horizontal metal sheet with uniform positive charge. The time period of the oscillation is {tex} T . {/tex} If the block is given a charge {tex} Q , {/tex} its time period of oscillation

remains same.

B

increases.

C

decreases.

D

increases if {tex} Q {/tex} is positive and decreases if {tex} Q {/tex} is negative.

Explanation

Q 13.    

Correct4

Incorrect-1

There is an electric field {tex} E {/tex} in {tex} x {/tex} -direction. If work done in moving a charge {tex} 0.2\mathrm { C } {/tex} through a distance of {tex} 2 \mathrm { m } {/tex} along a line making an angle of {tex} 60 ^ { \circ } {/tex} with {tex} x {/tex} -axis is {tex} 4.0 \mathrm { J } {/tex} . The value of {tex} E {/tex} is

A

{tex} \sqrt { 3 } \mathrm { N } / \mathrm { C } {/tex}

B

{tex}4 \mathrm { N } / \mathrm { C } {/tex}

C

{tex}5 \mathrm { N } / \mathrm { C } {/tex}

{tex}20 \mathrm { N } / \mathrm { C } {/tex}

Explanation

Q 14.    

Correct4

Incorrect-1

In electrolysis, the amount of mass deposited or liberated at an electrode is directly proportional to

amount of charge.

B

square of current.

C

concentration of electrolyte.

D

square of electric charge.

Explanation

Q 15.    

Correct4

Incorrect-1

The ratio of the forces between two small spheres with same charges when they are in air to when they are in a medium of dielectric constant {tex} K {/tex} is

A

{tex} 1 : K {/tex}

{tex} K : 1 {/tex}

C

{tex} 1 : K ^ { 2 } {/tex}

D

{tex} K ^ { 2 } : 1 {/tex}

Explanation

Q 16.    

Correct4

Incorrect-1

A charge {tex} Q {/tex} is divided into two parts of magnitude {tex} q {/tex} and {tex} Q - q . {/tex} If the coulomb repulsion between them when they are separated at some distance is to be maximum, the ratio of {tex} \frac { Q } { q } {/tex} should be

2

B

1{tex} / 2 {/tex}

C

4

D

1{tex} / 4 {/tex}

Explanation



Q 17.    

Correct4

Incorrect-1

There are two charges {tex} + 1 \mu C {/tex} and {tex} + 5 \mu C {/tex} . The ratio of the forces acting on them will be

A

{tex} 1 : 5 {/tex}

{tex} 1 : 1 {/tex}

C

{tex} 5 : 1 {/tex}

D

{tex} 1 : 25 {/tex}

Explanation

Q 18.    

Correct4

Incorrect-1

The electric potential {tex} V {/tex} is given as a function of distance {tex} x {/tex} (metre) by {tex} V = \left( 5 x ^ { 2 } + 10 x - 9 \right) {/tex} v. Magnitude of electric field at {tex} x = 1 {/tex} is

20{tex} \mathrm { V } / \mathrm { m } {/tex}

B

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

C

11{tex} \mathrm { V } / \mathrm { m } {/tex}

D

{tex} - 23 \mathrm { V } / \mathrm { m } {/tex}

Explanation

Q 19.    

Correct4

Incorrect-1

If specific resistance of a wire is {tex} \rho , {/tex} its volume is {tex} 3 \mathrm { m } ^ { 3 } , {/tex} and its resistance is 3 omhs, then its length will be

A

{tex} \sqrt { \frac { 1 } { \rho } } {/tex}

{tex} \frac { 3 } { \sqrt { \rho } } {/tex}

C

{tex} \frac { 1 } { \rho } \sqrt { 3 } {/tex}

D

{tex}\rho \sqrt { \frac { 1 } { \rho } } {/tex}

Explanation

Q 20.    

Correct4

Incorrect-1

Figure 13.34 shows the electric lines of force emerging from a charged body. If the electric field at {tex} A {/tex} and {tex} B {/tex}
are {tex} E _ { A } {/tex} and {tex} E _ { B } , {/tex} respectively, and if the displacement between {tex} A {/tex} and {tex} B {/tex} is {tex} r {/tex} then

A

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

{tex} E _ { A } < E _ { B } {/tex}

C

{tex} E _ { A } = \frac { E _ { B } } { r } {/tex}

D

{tex} E _ { A } = \frac { E _ { B } } { r ^ { 2 } } {/tex}

Explanation

Q 21.    

Correct4

Incorrect-1

The magnitude of electric feild intensity {tex} E {/tex} is such that, an electron of mass {tex}m {/tex} and {tex} e {/tex} placed in it would
experience an electrical force equal to its weight is given by

A

{tex} m g e {/tex}

{tex} \frac { m g } { e } {/tex}

C

{tex} \frac { e } { m g } {/tex}

D

{tex} \frac { e ^ { 2 } } { m ^ { 2 } } g {/tex}

Explanation

Q 22.    

Correct4

Incorrect-1

Figure 13.35 shows three point {tex}\mathrm {A, B\,and \, C}{/tex} in a region of uniform electric field {tex}\mathrm{\stackrel {\rightarrow } E}{/tex}. The line AB is perpendicular and BC is parallel to the field lines. Then which
of the following holds good. Where {tex} V _ { A } , V _ { B } , {/tex} and {tex} V _ { C } {/tex} , represent the electric potential at points {tex} A , B , {/tex} and {tex} C , {/tex} respectively.

A

{tex} V _ { A } = V _ { B } = V _ { C } {/tex}

{tex} V _ { A } = V _ { B } > V _ { C } {/tex}

C

{tex} V _ { A } = V _ { B } < V _ { C } {/tex}

D

{tex} V _ { A } > V _ { B } = V _ { C } {/tex}

Explanation

Q 23.    

Correct4

Incorrect-1

{tex} A B C {/tex} is an equilateral triangle. Charges {tex} + q {/tex} are placed at each corner. The electric field intensity at centroid {tex} O {/tex} will be

A

{tex} \frac { 1 } { 2 \pi \varepsilon _ { 0 } } \times \frac { q } { r ^ { 2 } } {/tex}

B

{tex} \frac { 1 } { 2 \pi \varepsilon _ { 0 } } \times \frac { 3 q } { r ^ { 2 } } {/tex}

C

{tex} \frac { 1 } { 2 \pi \varepsilon _ { 0 } } \times \frac { \sqrt { 3 } q } { r ^ { 2 } } {/tex}

Zero

Explanation

Q 24.    

Correct4

Incorrect-1

A charged particle of mass {tex} m {/tex} and charge {tex} q {/tex} is released from rest in an electric field of constant magnitude {tex} E {/tex} . The kinetic energy of the particle after a time {tex} t {/tex} is

A

{tex} \frac { E ^ { 2 } q ^ { 2 } t ^ { 2 } } { m } {/tex}

B

{tex} \frac { 2 E ^ { 2 } q ^ { 2 } t ^ { 2 } } { m } {/tex}

{tex} \frac { E ^ { 2 } q ^ { 2 } t ^ { 2 } } { 2 m } {/tex}

D

{tex} \frac { 4 E ^ { 2 } q ^ { 2 } t ^ { 2 } } { m } {/tex}

Explanation

Q 25.    

Correct4

Incorrect-1

Three charges {tex} Q , + q , {/tex} and {tex} + q {/tex} are placed at the vertices of a right angle triangle (isosceles triangle) as shown.
The net electrostatic energy of the configuration is zero, if {tex} Q {/tex} is equal to

A

{tex} \frac { - q } { 1 + \sqrt { 2 } } {/tex}

{tex} \frac { - 2 q } { 2 + \sqrt { 2 } } {/tex}

C

{tex} - 2 q {/tex}

D

{tex} + q {/tex}

Explanation