MCQ (Single Correct Answer)

1

Assertion (A): Equal amount of positive and negative charges are distributed uniformly on two halves of a thin circular ring as shown in figure. The resultant electric field at the centre O of the ring is along OC.

Reason (R): It is so because the net potential at $O$ is not zero.

CBSE 12th Physics Delhi Set 1 - 2024 Physics - Electrostatics Question 2 English

CBSE 12th Physics Delhi Set 1 - 2024
2

An electric dipole of length $$2 \mathrm{~cm}$$ is placed at an angle of $$30^{\circ}$$ with an electric field $$2 \times 10^5 \mathrm{~N} / \mathrm{C}$$. If the dipole experiences a torque of $$8 \times 10^{-3} \mathrm{~Nm}$$, the magnitude of either charge of the dipole, is

CBSE 12th Physics Delhi Set 1 - 2023
3

The magnitude of the electric field due to a point charge object at a distance of $$4.0 \mathrm{~m}$$ is $$9 \frac{\mathrm{N}}{\mathrm{C}}$$. From the same charged object the electric field of magnitude, $$16 \frac{\mathrm{N}}{\mathrm{C}}$$ will be at a distance of

CBSE 12th Physics Outside Delhi Set 1 - 2023
4

A point $$P$$ lies at a distance $$x$$ from the mid point of an electric dipole on its axis. The electric potential at point $$\mathrm{P}$$ is proportional to

CBSE 12th Physics Outside Delhi Set 1 - 2023
5

Beams of electrons and protons move parallel to each other in the same direction. They

CBSE 12th Physics Outside Delhi Set 1 - 2023
6

Assertion (A) : Work done in moving a charge around a closed path, in an electric field is always zero.

Reason (R) : Electrostatic force is a conservative force.

CBSE 12th Physics Outside Delhi Set 1 - 2023
7
A negatively charged object X is repelled by another charged object Y. However an object Z is attracted to object Y. Which of the following is the most possibility for the object Z?
CBSE 12th Physics (Term 1) Paper 2021-22
8
In an experiment three microscopic latex spheres are sprayed into a chamber and became charged with charges +3e, +5e and $$-$$3e respectively. All the three spheres came in contact simultaneously for a moment and got separated. Which one of the following are possible values for the final charge on the spheres?
CBSE 12th Physics (Term 1) Paper 2021-22
9
An object has charge of 1 C and gains 5.0 $$\times$$ 1018 electrons. The net charge on the object becomes -
CBSE 12th Physics (Term 1) Paper 2021-22
10
The electric potential V at any point (x, y, z) is given by V = 3x2 where x is in metres and V in volts. The electric field at the point (1 m, 0, 2m) is -
CBSE 12th Physics (Term 1) Paper 2021-22
11
Which of the diagrams correctly represents the electric field between two charged plates if a neutral conductor is placed in between the plates?
CBSE 12th Physics (Term 1) Paper 2021-22
12
The magnitude of electric field due to a point charge 2q, at distance r is E. Then the magnitude of electric field due to a uniformly charged thin spherical shell of radius R with total charge q at a distance $${r \over 2}(r > > R)$$ will be
CBSE 12th Physics (Term 1) Paper 2021-22
13
A square sheet of side 'a' is lying parallel to XY plate at z = a. The electric field in the region is $$\overrightarrow E = c{z^2}\widehat k$$. The electric flux through the sheet is
CBSE 12th Physics (Term 1) Paper 2021-22
14
Three charges q, $$-$$q and q0 are placed as shown in figure. The magnitude of the net force on the charge q0 at point O is $$\left[ {k = {1 \over {(4\pi { \in _0})}}} \right]$$

CBSE 12th Physics (Term 1) Paper 2021-22 Physics - Electrostatics Question 15 English
CBSE 12th Physics (Term 1) Paper 2021-22
15
A + 3.0 nC charge Q is initially at rest at a distance of r1 = 10 cm from a + 5.0 nC charge q fixed at the origin. The charge Q is moved away from q to a new position at r2 = 15 cm. In this process work done by the field is
CBSE 12th Physics (Term 1) Paper 2021-22
16
Four objects W, X, Y and Z, each with charge +q are held fixed at four points of a square of side d as shown in the figure. Objects X and Z are on the midpoints of the sides of the square. The electrostatic force exerted by object W on object X is F. Then the magnitude of the force exerted by object W on Z is

CBSE 12th Physics (Term 1) Paper 2021-22 Physics - Electrostatics Question 13 English
CBSE 12th Physics (Term 1) Paper 2021-22
17
Two charges 14 $$\mu$$C and $$-$$4 $$\mu$$C are placed at ($$-$$12 cm, 0, 0) and (12 cm, 0, 0) in an external electric field $$E = \left( {{B \over {{r^2}}}} \right)$$, where B = 1.2 $$\times$$ 106 N/(cm2) and r is in metres. The electrostatic potential energy of the configuration is
CBSE 12th Physics (Term 1) Paper 2021-22
18
Assertion (A) : A negative charge in an electric field moves along the direction of the electric field.

Reason (R) : On a negative charge a force acts in the direction of the electric field.
CBSE 12th Physics (Term 1) Paper 2021-22
19
Equipotentials at a large distance from a collection of charges whose total sum is not zero are -
CBSE 12th Physics (Term 1) Paper 2021-22
20
Four charges $$-$$q, $$-$$q, +q and +q are placed at the corners of a square of side 2 L is shown in figure. The electric potential at point A midway between the two charges +q and +q is -

CBSE 12th Physics (Term 1) Paper 2021-22 Physics - Electrostatics Question 12 English
CBSE 12th Physics (Term 1) Paper 2021-22

Subjective

1

(a) Four point charges of $1 \mu \mathrm{C},-2 \mu \mathrm{C}, 1 \mu \mathrm{C}$ and $-2 \mu \mathrm{C}$ are placed at the corners $\mathrm{A}, \mathrm{B}, \mathrm{C}$ and D respectively, of a square of side 30 cm . Find the net force acting on a charge of $4 \mu \mathrm{C}$ placed at the centre of the square.

OR

(b) Three point charges, 1 pC each, are kept at the vertices of an equilateral triangle of side 10 cm . Find the net electric field at the centroid of triangle.

CBSE 12th Physics Delhi Set 1 - 2024
2

(a) Define the term 'electric flux' and write its dimensions.

(b) A plane surface, in shape of a square of side 1 cm is placed in an electric field $\vec{E}=\left(100 \frac{\mathrm{~N}}{\mathrm{C}}\right) \hat{i}$ such that the unit vector normal to the surface is given by $\hat{n}=0.8 \hat{i}+0.6 \hat{k}$. Find the electric flux through the surface.

CBSE 12th Physics Delhi Set 1 - 2024
3

(a) (i) Draw equipotential surfaces for an electric dipole.

(ii) Two point charges $q_1$ and $q_2$ are located at $\overrightarrow{r_1}$ and $\vec{r}_2$ respectively in an external electric field $\vec{E}$. Obtain an expression for the potential energy of the system.

(iii) The dipole moment of a molecule is $10^{-30} \mathrm{Cm}$. It is placed in an electric field $\vec{E}$ of $10^5 \mathrm{~V} / \mathrm{m}$ such that its axis is along the electric field. The direction of $\vec{E}$ is suddenly changed by $60^{\circ}$ at an instant. Find the change in the potential energy of the dipole, at that instant.

OR

(b) (i) A thin spherical shell of radius R has a uniform surface charge density $\sigma$. Using Gauss' law, deduce an expression for electric field (i) outside and (ii) inside the shell.

(ii) Two long straight thin wires AB and CD have linear charge densities $10 \mu \mathrm{C} / \mathrm{m}$ and $-20 \mu \mathrm{C} / \mathrm{m}$, respectively. They are kept parallel to each other at a distance 1 m . Find magnitude and direction of the net electric field at a point midway between them.

CBSE 12th Physics Delhi Set 1 - 2024
4

Depict the orientation of an electric dipole in (a) stable and (b) unstable equilibrium in an external uniform electric field. Write the potential energy of the dipole in each case.

CBSE 12th Physics Delhi Set 1 - 2023
5

(a) (i) Use Gauss' law to obtain an expression for the electric field due to an infinitely long thin straight wire with uniform linear charge density $$\lambda$$.

(ii) An infinitely long positively charged straight wire has a linear charge density $$\lambda$$. An electron is revolving in a circle with a constant speed $$v$$ such that the wire passes through the centre, and is perpendicular to the plane, of the circle. Find the kinetic energy of the electron in terms of magnitudes of its charge and linear charge density $$\lambda$$ on the wire.

(iii) Draw a graph of kinetic energy as a function of linear charge density $$\lambda$$.

OR

(b) (i) Consider two identical point charges located at points $$(0,0)$$ and $$(a, 0)$$.

(1) Is there a point on the line joining them at which the electric field is zero?

(2) Is there a point on the line joining them at which the electric potential is zero?

Justify your answers for each case.

(ii) State the significance of negative value of electrostatic potential energy of a system of charges.

Three charges are placed at the corners of an equilateral triangle $$A B C$$ of side $$2.0 \mathrm{~m}$$ as shown in figure. Calculate the electric potential energy of the system of three charges.

CBSE 12th Physics Outside Delhi Set 1 - 2023 Physics - Electrostatics Question 8 English

CBSE 12th Physics Outside Delhi Set 1 - 2023
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