ELECTRIC FIELDS AND CHARGES MCQs for JEE PHYSICS — Hard

1 Hard

1 of 10

Application +4 | -1

The magnitude of the average electric field normally present in the atmosphere just above the surface of the earth is about

150\,N/C,

directed inward towards the center of the earth. This gives the total net surface charge carried by the earth to be:

\left[ {{\text{Given}}\,{\varepsilon _0} = 8.85 \times {{10}^{ - 12}}\,{C^2}/N - {m^2},\,{R_E} = 6.37 \times {{10}^6}\,m} \right]

View answer and explanation

Correct option: C

- 680\,kC

Option C (

- 680\,kC

) is correct because the total net surface charge is calculated using Gauss's law and the given electric field, directed inward.

2 Hard

2 of 10

Analyzing +4 | -1

Two equal negative charges

-q

are fixed at the points

(0, a)

and

(0,-a)

on the

y

-axis. A positive charge

Q

is released from rest from the point

(2 a, 0 )

on the

x

-axis. The charge will

View answer and explanation

Correct option: D

Execute oscillatory motion but not S.H.M

Option D (Execute oscillatory motion but not S.H.M) is correct because the force on the charge Q is not proportional to its displacement from the origin, thus it oscillates but not in simple harmonic motion.

3 Hard

3 of 10

Application +4 | -1

Let there be a spherically symmetric charge distribution with charge density varying as

\rho(r)=\rho_0\left[\frac{2}{3}-\frac{2 r}{R}\right]

upto

r=R

and

\rho(r)=0

for

r>R

, where

r

is the distance from origin. The electric field at a distance

r(r < R)

from the origin is given by:

View answer and explanation

Correct option: B

\frac{\rho_0 r}{\varepsilon_0}\left[\frac{2}{9}-\frac{r}{2 R}\right]

Option B is correct because the electric field is calculated using Gauss's law by integrating the charge density over a spherical volume and then applying the formula E = Kq/r².

4 Hard

4 of 10

Analyzing +4 | -1

Given below are two statements:
Statement I An electric diploe is placed at the centre of a hollow sphere. The flux of electric field through the sphere is zero but the electric field is not zero anywhere in the sphere.
Statement II If

R

is the radius of a solid metallic sphere and

Q

be the total charge on it. The electric field at any point on the spherical surface of radius

r( < R)

is zero but the electric flux passing through this closed spherical surface of radius

r

is not zero.
In the light of the above statements, choose the correct answer from the options given below.

View answer and explanation

Correct option: B

Statement I is true but Statement II is false.

Option B is correct. Statement I is true because the net charge of a dipole is zero, resulting in zero flux, but the electric field is non-zero. Statement II is false because the electric field inside a charged solid sphere is not zero.

5 Hard

5 of 10

Understanding +4 | -1

Select the correct statements from the following:

I. The electric field due to a charge outside the Gaussian surface contributes zero net flux through the surface.

II. Total flux linked with a closed body, enclosing any charges will be zero.

III. Total electric flux, if a dipole is enclosed by a surface is zero.

View answer and explanation

Correct option: C

I and III

Option C (I and III) is correct. Statement I is correct because of Gauss's law, and Statement III is correct because a dipole has a net charge of zero.

6 Hard

6 of 10

Analyzing +4 | -1

Given below are two statements:
Statement I An electric diploe is placed at the centre of a hollow sphere. The flux of electric field through the sphere is zero but the electric field is not zero anywhere in the sphere.
Statement II If

R

is the radius of a solid metallic sphere and

Q

be the total charge on it. The electric field at any point on the spherical surface of radius

r( < R)

is zero but the electric flux passing through this closed spherical surface of radius

r

is not zero.
In the light of the above statements, choose the correct answer from the options given below.

View answer and explanation

Correct option: B

Statement I is true but Statement II is false.

Option B is correct. Statement I is true because the net charge of a dipole is zero, resulting in zero flux, but the electric field is non-zero. Statement II is false because the electric field inside a charged solid sphere is not zero.

7 Hard

7 of 10

Understanding +4 | -1

Statement-1:

\overrightarrow{{E}}

in outside velocity of a conductor depends only on the local charge density

\alpha

.
Statement-2:

\overrightarrow{{E}}

in outside vicinity of a conductor is given by

\frac{\sigma}{\varepsilon_0}

.

View answer and explanation

Correct option: D

Statement-1 is false, Statement-2 is true

Option D (Statement-1 is false, Statement-2 is true) is correct because the electric field outside a conductor depends on the overall charge distribution, and Statement-2 correctly gives the electric field near the surface.

8 Hard

8 of 10

Analyzing +4 | -1

Given below are two statements: one is labelled
as Assertion (A) and the other is labelled as
Reason (R).

Assertion (A): Net dipole moment of a polar
linear isotropic dielectric substance is not zero
even in the absence of an external electric field.

Reason (R): In absence of an external electric
field, the different permanent dipoles of a polar
dielectric substance are oriented in random
directions.

In the light of the above statements, choose the
most appropriate answer from the options given
below:

View answer and explanation

Correct option: D

(A) is not correct but (R) is correct

Option D ((A) is not correct but (R) is correct) is correct. A polar dielectric substance has randomly oriented dipoles resulting in a net dipole moment of zero in the absence of an external electric field, and the reason correctly states this random orientation.

9 Hard

9 of 10

Application +4 | -1

A particle of charge

-q

and mass

m

moves in a circle of radius

r

around an infinitely long line charge of linear charge density

+\lambda.

Then time period will be given as:

(Consider

k

as Coulomb's constant)

View answer and explanation

Correct option: C

T=2 \pi r \sqrt{\frac{m}{2 k \lambda q}}

Option C (

T=2 \pi r \sqrt{\frac{m}{2 k \lambda q}}

) is correct because it correctly equates the centripetal force with the electrostatic force and solves for the time period.

10 Hard

10 of 10

Analyzing +4 | -1

Given below are two statements:
Statement I An electric diploe is placed at the centre of a hollow sphere. The flux of electric field through the sphere is zero but the electric field is not zero anywhere in the sphere.
Statement II If

R

is the radius of a solid metallic sphere and

Q

be the total charge on it. The electric field at any point on the spherical surface of radius

r( < R)

is zero but the electric flux passing through this closed spherical surface of radius

r

is not zero.
In the light of the above statements, choose the correct answer from the options given below.

View answer and explanation

Correct option: B

Statement I is true but Statement II is false.

Option B is correct because Statement I is true (flux through the sphere is zero due to the dipole's net charge being zero), but Statement II is false (electric field inside a charged solid sphere is non-zero).

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Electric fields and charges practice · Hard

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