Electrostatic Potential and Capacitance Class 12 Physics MCQs 2026-27

Class 12 Physics • Chapter 2 • MCQs

Electrostatic Potential and Capacitance Class 12 Physics MCQs with Answers

40 original, syllabus-focused multiple-choice questions covering electric potential, potential energy, equipotential surfaces, conductors, dielectrics, capacitance, capacitor combinations and stored energy for CBSE 2026–27.

Practice note: These are original CBSE-style practice MCQs, not official CBSE questions and not predictions of the board paper. Solve first, then check the answer and explanation.

Chapter 2 MCQs — Coverage Map

This set is deliberately broader than a formula-only quiz. It covers definitions, signs, physical meaning, application, numerical reasoning and common exam traps. The scope follows the current Chapter 2 syllabus rather than adding unrelated competitive-exam topics.

• Electric potential and potential difference
• Potential due to point charge, dipole and system of charges
• Equipotential surfaces
• Potential energy of charges and electric dipole
• Conductors, free charges and bound charges
• Dielectrics and electric polarisation
• Capacitance and parallel-plate capacitors
• Series and parallel combinations
• Dielectric insertion with battery connected or disconnected
• Energy stored in a capacitor

MCQs with Answers and Explanations

1. Electric potential at a point is defined as:

A. Force acting on a unit positive charge

B. Work done per unit positive test charge in bringing it from infinity to the point

C. Energy stored per unit volume

D. Electric field multiplied by distance only

Answer: B

Explanation: With potential at infinity chosen as zero, V = W/q0. Potential is a scalar quantity.

2. The SI unit of electric potential is:

A. N/C

B. C/N

C. J/C

D. J·C

Answer: C

Explanation: One volt is one joule per coulomb.

3. The electric potential due to a point charge q at distance r in vacuum is:

A. kq/r²

B. kq/r

C. kr/q

D. kq²/r

Answer: B

Explanation: Taking potential at infinity as zero, V = (1/4πε0)q/r = kq/r.

4. If the charge producing a potential is doubled while the distance is unchanged, the potential becomes:

A. Half

B. Double

C. Four times

D. Unchanged

Answer: B

Explanation: Since V ∝ q, doubling q doubles V.

5. If the distance from a point charge is doubled, its potential becomes:

A. Four times

B. Twice

C. Half

D. One-fourth

Answer: C

Explanation: V ∝ 1/r, so doubling r halves the potential.

6. Electric potential is:

A. A vector

B. A scalar

C. Always positive

D. Always zero inside a charge distribution

Answer: B

Explanation: Potential has magnitude and sign but no direction. Contributions from several charges are added algebraically.

7. The potential at the midpoint of two equal positive charges is:

A. Zero

B. Positive and non-zero

C. Negative

D. Always infinite

Answer: B

Explanation: Potentials from the two positive charges add. The electric field may cancel at the midpoint, but potential does not.

8. At a point where electric potential is zero, the electric field must be:

A. Zero

B. Infinite

C. Not necessarily zero

D. Always uniform

Answer: C

Explanation: Field depends on the spatial gradient of potential, E = −∇V. A point can have V = 0 while the gradient is non-zero.

9. The work done by the electrostatic field in moving a charge q from A to B is:

A. q(VB−VA)

B. q(VA−VB)

C. q(VA+VB)

D. q/(VA−VB)

Answer: B

Explanation: The field does work equal to the decrease in electrostatic potential energy: Wfield = q(VA−VB).

10. Which statement about an equipotential surface is correct?

A. Potential varies from point to point on it

B. Moving a charge along it requires non-zero electrostatic work

C. The potential difference between any two points on it is zero

D. Electric field is always parallel to it

Answer: C

Explanation: Every point on an equipotential surface has the same potential, so ΔV = 0.

11. Electric field lines are perpendicular to an equipotential surface because:

A. Potential is a vector

B. A tangential electric field would produce non-zero work along the equipotential

C. Equipotential surfaces carry no charge in every case

D. Electric field is always zero

Answer: B

Explanation: Along an equipotential, no work is done. Therefore the electric field has no tangential component and is normal to the surface.

12. The potential energy of two point charges q₁ and q₂ separated by r is:

A. kq1q2/r²

B. kq1q2/r

C. k(q1+q2)/r

D. kr/(q1q2)

Answer: B

Explanation: With zero reference at infinity, U = kq1q2/r.

13. For two like charges, their electrostatic potential energy is:

A. Negative

B. Positive

C. Always zero

D. Independent of separation

Answer: B

Explanation: For like charges, q1q2 > 0, so U is positive with the usual infinity reference.

14. The potential energy of an electric dipole in a uniform electric field is:

A. pE cosθ

B. −pE cosθ

C. p/E

D. −p/E

Answer: B

Explanation: U = −p·E = −pE cosθ.

15. An electric dipole is in stable equilibrium in a uniform electric field when its dipole moment is:

A. Perpendicular to E

B. Opposite to E

C. Parallel to E

D. At 45° to E

Answer: C

Explanation: Stable equilibrium corresponds to minimum potential energy, U = −pE, which occurs at θ = 0°.

16. Inside the material of an ideal conductor in electrostatic equilibrium, the electric field is:

A. Maximum

B. Zero

C. Uniform but non-zero

D. Infinite

Answer: B

Explanation: Free charges rearrange until the net electric field inside the conducting material becomes zero.

17. In electrostatic equilibrium, excess charge on an isolated conductor resides:

A. Only at the centre

B. Throughout the bulk uniformly in every shape

C. On its surface

D. Nowhere

Answer: C

Explanation: Excess free charge resides on the conductor's surface in electrostatic equilibrium; its surface distribution depends on geometry.

18. A conductor in electrostatic equilibrium is:

A. An equipotential body

B. Always negatively charged

C. Always positively charged

D. Always an insulator

Answer: A

Explanation: Since E = 0 inside the conductor, there is no potential difference between any two points of the conductor.

19. A dielectric is best described as a material that:

A. Has no atoms or molecules

B. Becomes perfectly conducting when placed in an electric field

C. Can become polarised in an electric field and normally has very low free-charge conduction

D. Always removes all electric field

Answer: C

Explanation: Dielectrics are insulating materials whose bound charges can shift slightly, producing polarisation.

20. When a dielectric is inserted between the plates of a capacitor and completely fills the gap, the capacitance becomes:

A. C/K

B. KC

C. C + K

D. C − K

Answer: B

Explanation: For relative permittivity K, C' = KC when the dielectric completely fills the region between the plates.

21. The capacitance of an isolated capacitor depends directly on:

A. The charge currently stored

B. The potential difference currently applied

C. Its geometry and the material between its conductors

D. The mass of the plates

Answer: C

Explanation: Capacitance is determined by geometry and dielectric properties, not by Q or V independently.

22. For a parallel-plate capacitor in vacuum, capacitance is:

A. ε0d/A

B. ε0A/d

C. A/(ε0d)

D. d/(ε0A)

Answer: B

Explanation: C = ε0A/d, neglecting fringing.

23. If the plate area of a parallel-plate capacitor is doubled while separation remains unchanged, its capacitance:

A. Halves

B. Doubles

C. Becomes four times

D. Remains unchanged

Answer: B

Explanation: From C = εA/d, capacitance is directly proportional to plate area.

24. If the plate separation of a parallel-plate capacitor is doubled, its capacitance:

A. Doubles

B. Halves

C. Becomes four times

D. Remains unchanged

Answer: B

Explanation: C ∝ 1/d.

25. Three capacitors C₁, C₂ and C₃ connected in parallel have equivalent capacitance:

A. C1 + C2 + C3

B. 1/C1 + 1/C2 + 1/C3

C. C1C2C3

D. C1/(C2+C3)

Answer: A

Explanation: Parallel capacitors have the same voltage and their charges add, giving Ceq = ΣCi.

26. For capacitors connected in series, which quantity has the same magnitude on each capacitor?

A. Potential difference

B. Charge

C. Capacitance

D. Stored energy

Answer: B

Explanation: In a simple series combination, each capacitor carries the same magnitude of charge.

27. Two capacitors of 2 μF and 3 μF are connected in parallel. Their equivalent capacitance is:

A. 1.2 μF

B. 2.5 μF

C. 5 μF

D. 6 μF

Answer: C

Explanation: In parallel, Ceq = 2 + 3 = 5 μF.

28. Two capacitors of 2 μF and 3 μF are connected in series. Their equivalent capacitance is:

A. 5 μF

B. 1.2 μF

C. 6 μF

D. 0.5 μF

Answer: B

Explanation: Ceq = (2×3)/(2+3) = 1.2 μF.

29. A capacitor of capacitance 4 μF is connected to a 10 V battery. Its charge is:

A. 0.4 μC

B. 4 μC

C. 40 μC

D. 400 μC

Answer: C

Explanation: Q = CV = 4 μF × 10 V = 40 μC.

30. A 2 μF capacitor is charged to 20 V. The energy stored is:

A. 2×10⁻⁴ J

B. 4×10⁻⁴ J

C. 8×10⁻⁴ J

D. 4×10⁻³ J

Answer: B

Explanation: U = ½CV² = ½(2×10−6)(20²) = 4×10−4 J.

31. Which expression for capacitor energy is equivalent to the other two?

A. ½CV²

B. ½QV

C. Q²/(2C)

D. All of these

Answer: D

Explanation: Since Q = CV, all three forms are mathematically equivalent.

32. A charged capacitor is disconnected from its battery. A dielectric of constant K is then completely inserted. Which quantity remains constant?

A. Potential difference

B. Charge

C. Capacitance

D. Stored energy

Answer: B

Explanation: With the capacitor isolated, charge cannot flow, so Q remains constant. The capacitance increases and the voltage decreases.

33. A dielectric is inserted fully while the capacitor remains connected to an ideal battery. Which quantity remains constant?

A. Charge

B. Potential difference

C. Stored energy

D. Electric field in every possible geometry

Answer: B

Explanation: The battery fixes the potential difference. Since C increases by K, Q also increases by K.

34. An isolated capacitor has capacitance C and voltage V. A dielectric of constant K is inserted fully. Its new voltage is:

A. KV

B. V/K

C. V + K

D. V

Answer: B

Explanation: Q is fixed and C becomes KC. Therefore V' = Q/(KC) = V/K.

35. For an isolated charged capacitor, a dielectric of constant K is inserted fully. The stored energy becomes:

A. KU

B. U/K

C. U

D. K²U

Answer: B

Explanation: Q remains fixed and U = Q²/(2C). Since C becomes KC, energy becomes U/K.

36. For a capacitor remaining connected to a battery, a dielectric of constant K is inserted fully. The stored energy becomes:

A. U/K

B. KU

C. U

D. U/K²

Answer: B

Explanation: The battery keeps V constant, while C becomes KC. From U = ½CV², U becomes KU.

37. A point charge produces a potential of 900 V at a distance of 0.20 m in vacuum. Taking k = 9×10⁹ N m²/C², the charge is:

A. 2×10⁻⁸ C

B. 2×10⁻⁷ C

C. 2×10⁻⁹ C

D. 2×10⁻⁶ C

Answer: A

Explanation: q = Vr/k = (900×0.20)/(9×109) = 2×10−8 C.

38. A charge of 4 μC moves from 50 V to 120 V. Its change in potential energy is:

A. 1.4×10⁻⁴ J

B. 2.8×10⁻⁴ J

C. 4.8×10⁻⁴ J

D. 2.8×10⁻³ J

Answer: B

Explanation: ΔU = qΔV = 4×10−6(120−50) = 2.8×10−4 J.

39. A capacitor remains connected to a battery while its plate separation is doubled. Which set is correct?

A. C doubles, Q doubles, V constant

B. C halves, Q halves, V constant

C. C halves, Q constant, V doubles

D. C constant, Q halves, V halves

Answer: B

Explanation: Doubling d makes C = εA/d halve. The connected battery keeps V fixed, so Q = CV also halves.

40. Which statement is correct about the electric field and potential?

A. Electric field always points toward increasing potential

B. Electric field points in the direction of decreasing potential

C. Potential is always zero where electric field is non-zero

D. Electric field and potential have the same physical dimensions

Answer: B

Explanation: The relation E = −∇V shows that the electric field points toward decreasing potential.

Quick Answer Key

1-B, 2-C, 3-B, 4-B, 5-C, 6-B, 7-B, 8-C, 9-B, 10-C, 11-B, 12-B, 13-B, 14-B, 15-C, 16-B, 17-C, 18-A, 19-C, 20-B, 21-C, 22-B, 23-B, 24-B, 25-A, 26-B, 27-C, 28-B, 29-C, 30-B, 31-D, 32-B, 33-B, 34-B, 35-B, 36-B, 37-A, 38-B, 39-B, 40-B.

High-Value MCQ Traps

• Potential is scalar: add potential contributions algebraically.
• V = 0 does not automatically mean E = 0.
• Equipotential means ΔV = 0: therefore no electrostatic work is done along it.
• Series: same charge magnitude; voltages generally differ.
• Parallel: same voltage; charges generally differ.
• Battery connected: V is fixed by the ideal battery.
• Battery disconnected: Q is fixed for an isolated capacitor.
• Dielectric fully inserted: C becomes KC.
• Energy formula: choose the form that matches what remains fixed.
• Do not confuse: potential V with potential energy U.

How to Score Yourself

For learning purposes, use the following simple diagnostic rather than treating it as a prediction of board marks:

• 36–40: concepts and formula application are mostly secure; move to numericals and case-based practice.
• 30–35: review the explanations for missed questions, then attempt timed practice.
• 20–29: revise the chapter notes and important questions before repeating the MCQs.
• Below 20: rebuild the chapter from definitions and core formulas, then retry the set.

Chapter 2 Resource Path

1. Electrostatic Potential and Capacitance — Chapter Hub
2. Complete Notes
3. Important Questions with Answers
4. This page: MCQs with Answers

Official Curriculum Reference

Use the current official CBSE Class XII Physics curriculum as the authority for syllabus scope. The current Chapter 2 scope includes potential, potential difference, potential due to charges and dipoles, equipotential surfaces, potential energy, conductors, dielectrics, capacitors, series/parallel combinations, parallel-plate capacitance and capacitor energy formulae.

CBSE Class XII Physics Curriculum 2026–27

CBSE Class XII Sample Question Papers & Marking Schemes 2026–27

Next step: After MCQ practice, use chapter numericals and case-based questions to test whether you can apply the same concepts in unfamiliar situations.