Class 12 Physics Chapter 2 Electrostatic Potential Capacitance Solved Question and Answers

1 What is the number of electrons in 100 g water?

A 3.35 × 10²⁴

B 3.35 × 10²⁵

C 6.02 × 10²³

D None of these

View Answer

Answer:3.35 × 10²⁴

2 The electric potential of earth is taken as:

A zero

B infinity

C unity

D None of these

View Answer

Answer:zero

3 Which of the following statement is true?

A Electrostatic force is a conservative force.

B Potential at a point is the work done per unit charge in bringing a charge from any point to infinity.

C Electrostatic force is non-conservative

D Potential is the productof charge and work.

View Answer

Answer:Electrostatic force is a conservative force.

4 A capacitor is charged by using a battery which is then disconnected. A dielectric slab then slipped between the plates, which results in

A reduction of charge on the plates and increase of potential difference across the plates.

B increase in the potential difference across the plate, reduction in stored energy, but no change in the charge on the plates.

C decrease in the potential difference across the plates, reduction in the stored energy, but no change in the charge on the plates.

D none of these

View Answer

Answer:decrease in the potential difference across the plates, reduction in the stored energy, but no change in the charge on the plates.

5 The work done in bringing a unit positive charge from infinite distance to a point at distance x from a positive charge Q is W. Then the potential at that point is

A WQ/x

B W

C W/x

D WQ

View Answer

Answer:W

6 Acapacitor of 4 pF is connected as shown in the circuit. The internal resistance of the battery is 0.5

Q. The amount of charge on the capacitor plates will be

Electrostatic Potential and Capacitance

A 0

B 4

C 16 μC

D 8 μC

View Answer

Answer:8 μC

7 Two metal plates form a parallel plate capacitor. The distance between the plates is d. A metal sheet of thickness d/2 and of the same area is introduced between the plates. What is the ratio of the capacitance in the two cases?

A 2 : 1

B 3 : 1

C 2 : 1

D 5 : 1

View Answer

Answer:2 : 1

8 Three charges Q, +q and +q are placed at the vertices of an equilateral triangle of side l as shown in the figure. If the net electrostatic energy of the system is zero, then Q is equal to

Electrostatic Potential and Capacitance

A -q

B +q

C zero

D –q/2

View Answer

Answer:–q/2

9 A parallel plate condenser is connected with the terminals of a battery. The distance between the plates is 6mm. If a glass plate (dielectric constant K = 9) of 4.5 mm is introduced between them, then the capacity will become

A 2 times.

B the same.

C 3 times.

D 4 times.

View Answer

Answer:3 times.

10 The radii of two metallic spheres A and B are r₁ and r₂ respectively (r₁ > r₂). They are connected by a thin wire and the system is given a certain charge. The charge will be greater

A on the surface of the sphere B.

B on the surface of the sphere A.

C equal on both.

D zero on both.

View Answer

Answer:on the surface of the sphere A.

11 64 drops each having the capacity C and potential V are combined to form a big drop. If the charge on the small drop is q, then the charge on the big drop will be

A 2q

B 4q

C 16q

D 64q

View Answer

Answer:64q

12 Two small spheres each carrying a charge q are placed r metre apart. If one of the spheres is taken around the other one in a circular path of radius r, the work done will be equal to

A force between them × r

B force between them × 2πr

C force between them/2πr

D zero

View Answer

Answer:zero

13 If a unit positive charge is taken from one point to another over an equipotential surface, then

A work is done on the charge.

B work is done by the charge.

C work done is constant.

D no work is done.

View Answer

Answer:no work is done.

14 The electrostatic force between the metal plates of an isolated parallel plate capacitor C having a charge Q and area A, is

A proportional to the square root of the distance between the plates.

B linearly proportional to the distance between the plates.

C independent of the distance between the plates.

D inversely proportional to the distance between the plates.

View Answer

Answer:independent of the distance between the plates.

15 Which of the following options are correct? If a conductor has a potential V 4- 0 and there are no charges anywhere else outside, then

A there must not be charges on the surface or inside itself.

B there cannot be any charge in the body of the conductor.

C there must be charges only on the surface.

D there must be charges inside the surface.

View Answer

Answer:there cannot be any charge in the body of the conductor.

16 Which of the following options is correct? In a region of constant potential

A the electric field is uniform.

B the electric field is zero.

C there can be charge inside the regiofi.

D the electric field shall necessarily change if a charge is placed outside the region.

View Answer

Answer:the electric field is zero.

17 v Figure shows the electric lines of force emerging from a charged body. If the electric field at A and B are EA and EB respectively and if the displacement between A and B is r then

Electrostatic Potential and Capacitance

A E_A > E_B

B E_A < E_B

C E_A = E_B/r

D E_A = E_B /r²

View Answer

Answer:E_A > E_B

18 A conductor with a positive charge

A is always at +ve potential.

B is always at zero potential.

C is always at negative potential.

D may be at +ve, zero or -ve potential.

View Answer

Answer:may be at +ve, zero or -ve potential.

19 A capacitor is charged by a battery. The battery is removed and another identical uncharged capacitor is connected in parallel. The total electrostatic energy of resulting system

A increases by a factor of 4.

B decreases by a factor of 2.

C remains the same.

D increases by a factor of 2.

View Answer