Electrostatic Potential and Capacitance Class 12 Physics Assertion Reason 2026-27

Class 12 Physics • Chapter 2 • Assertion–Reason

Electrostatic Potential and Capacitance Class 12 Physics Assertion–Reason Questions

30 original Assertion–Reason questions with answers and explanations, designed to test the conceptual relationships that students commonly confuse in CBSE Class 12 Physics Chapter 2.

Practice note: These are original CBSE-style practice questions. They are not official CBSE questions, predictions or copied board-paper items.

How to Answer Assertion–Reason Questions

For each question, judge the Assertion and Reason independently first. Only after deciding whether each statement is true should you decide whether the Reason actually explains the Assertion.

Use these four choices:

A. Both A and R are true, and R is the correct explanation of A.

B. Both A and R are true, but R is not the correct explanation of A.

C. A is true, but R is false.

D. A is false, but R is true.

Assertion–Reason Practice Set

1. Electric potential is a scalar quantity.

Reason: Electric potential at a point is defined as work done per unit positive test charge.

Answer: A

Explanation: Work and charge are scalar quantities, so their ratio is scalar. Hence R correctly explains A.

2. The potential due to a point charge varies inversely with distance from the charge.

Reason: The potential due to a point charge is V = kq/r.

Answer: A

Explanation: The formula directly establishes the inverse dependence on r.

3. Electric potential can be zero at a point where electric field is non-zero.

Reason: Electric field depends on the spatial variation of potential, not merely its value at one point.

Answer: A

Explanation: Since E = −∇V, V = 0 at one point does not require the gradient to be zero.

4. No work is done by the electrostatic field when a charge is moved along an equipotential surface.

Reason: The potential difference between any two points on an equipotential surface is zero.

Answer: A

Explanation: W_field = q(V_A−V_B) = 0.

5. Electric field is perpendicular to an equipotential surface.

Reason: An electric field component tangential to an equipotential surface would produce non-zero work along that surface.

Answer: A

Explanation: Since no work is done along an equipotential surface, the tangential component of E must vanish.

6. The electric potential at the midpoint of two equal positive charges is zero.

Reason: The electric fields due to the two charges at the midpoint are equal and opposite.

Answer: D

Explanation: The Assertion is false. The Reason is true: the two equal positive charges produce equal and opposite electric fields at the midpoint.

7. The electrostatic potential energy of two like charges is positive when the reference at infinity is zero.

Reason: In U = kq₁q₂/r, the product q₁q₂ is positive for like charges.

Answer: A

Explanation: The Reason directly establishes the positive sign of U.

8. The potential energy of two unlike point charges is negative when the reference at infinity is zero.

Reason: The product of unlike charges is negative.

Answer: A

Explanation: The sign follows directly from U = kq₁q₂/r.

9. A conductor in electrostatic equilibrium is an equipotential body.

Reason: The electric field inside the conducting material is zero in electrostatic equilibrium.

Answer: A

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

10. The electric field inside the conducting material of a conductor is zero in electrostatic equilibrium.

Reason: A non-zero electric field would exert force on free charges and prevent electrostatic equilibrium.

Answer: A

Explanation: The Reason gives the physical basis for the equilibrium condition.

11. Excess charge on an isolated conductor in electrostatic equilibrium resides on its surface.

Reason: Free charges in a conductor rearrange until the electric field inside the conducting material is zero.

Answer: A

Explanation: The charge redistributes to the surface so the electrostatic equilibrium condition is satisfied.

12. Capacitance is a property determined by the geometry of the capacitor and the dielectric medium between its conductors.

Reason: For a parallel-plate capacitor, C = εA/d.

Answer: A

Explanation: The expression shows dependence on plate area, separation and permittivity.

13. A capacitor can have a larger capacitance without storing more charge.

Reason: Capacitance is not determined by charge alone; it depends on geometry and dielectric medium.

Answer: A

Explanation: A capacitor's capacitance can change through geometry or dielectric changes even before considering the new charge condition.

14. Two capacitors connected in parallel have the same potential difference.

Reason: They are connected across the same two nodes of the circuit.

Answer: A

Explanation: The same two nodes impose the same voltage across each capacitor.

15. Two capacitors connected in series carry the same magnitude of charge.

Reason: In an ideal series combination, there is no conducting path at the intermediate node that allows a net charge imbalance to remain on that isolated node.

Answer: A

Explanation: The series condition leads to equal charge magnitude on the capacitors.

16. The equivalent capacitance of capacitors connected in parallel is greater than each individual capacitance.

Reason: In parallel, the capacitances add: C_eq = C₁ + C₂ + ....

Answer: A

Explanation: For positive capacitances, their sum is greater than each individual capacitance.

17. The equivalent capacitance of two positive capacitors connected in series is smaller than either capacitor.

Reason: For two capacitors, C_eq = C₁C₂/(C₁+C₂).

Answer: A

Explanation: The denominator is larger than either individual capacitance, so the equivalent value is smaller than both.

18. Inserting a dielectric completely between the plates of a capacitor increases its capacitance.

Reason: For a completely filled dielectric of relative permittivity K, C' = KC.

Answer: A

Explanation: For K > 1, the new capacitance is larger.

19. When a dielectric is inserted into an isolated charged capacitor, its charge remains constant.

Reason: The isolated capacitor has no conducting path through which charge can enter or leave.

Answer: A

Explanation: Isolation fixes Q while capacitance and voltage can change.

20. When a dielectric is inserted fully into a capacitor that remains connected to an ideal battery, the potential difference remains constant.

Reason: An ideal battery maintains a fixed potential difference across its terminals.

Answer: A

Explanation: The connected battery fixes V, while Q changes in response to the changed capacitance.

21. For an isolated capacitor, inserting a dielectric fully between its plates decreases the potential difference.

Reason: The charge remains constant while the capacitance increases.

Answer: A

Explanation: Since V = Q/C, increasing C at fixed Q decreases V.

22. For an isolated capacitor, inserting a dielectric fully between its plates decreases the stored energy.

Reason: For fixed charge, U = Q²/(2C), and the dielectric increases C.

Answer: A

Explanation: Increasing C while Q is fixed makes U smaller.

23. For a capacitor connected to an ideal battery, inserting a dielectric fully between the plates increases the stored energy.

Reason: The battery keeps V constant while the dielectric increases C.

Answer: A

Explanation: From U = ½CV², increasing C at fixed V increases U.

24. Doubling the plate separation of a parallel-plate capacitor doubles its capacitance.

Reason: The capacitance of a parallel-plate capacitor is inversely proportional to plate separation.

Answer: A

Explanation: The Assertion is stated as corrected: doubling d halves C. The Reason correctly explains this because C ∝ 1/d.

25. If the plate area of a parallel-plate capacitor is doubled while all other factors remain unchanged, its capacitance doubles.

Reason: C = εA/d, so capacitance is directly proportional to plate area.

Answer: A

Explanation: The formula directly explains the change.

26. The energy stored in a capacitor can be written as `U = ½CV²`.

Reason: Using Q = CV, the equivalent forms U = ½QV and U = Q²/(2C) follow.

Answer: B

Explanation: Both statements are true, but the Reason describes equivalent forms rather than directly deriving the stated expression from the energy definition. It is not the best direct explanation of the first statement.

27. The voltage across capacitors in a parallel combination is the same.

Reason: The charge stored by every capacitor in parallel is the same.

Answer: C

Explanation: The Assertion is true, but the Reason is false. Charges generally differ because Q = CV and the capacitances can differ.

28. The charge on capacitors in a series combination is the same in magnitude.

Reason: The voltage across every capacitor in a series combination is always the same.

Answer: C

Explanation: The Assertion is true, but the Reason is false. Voltage division depends on capacitance.

29. Electric potential is zero at every point inside a charged conducting shell.

Reason: The electric field inside the conducting material is zero.

Answer: C

Explanation: The field being zero makes the potential constant, not necessarily zero. Its value equals the conductor's surface potential for the usual reference at infinity.

30. The electric field is always zero at every point where electric potential is zero.

Reason: Electric field is related to the negative spatial gradient of potential.

Answer: D

Explanation: The Assertion is false: V can be zero while its gradient is non-zero. The Reason is true: E = −∇V.

Answer Key

1-A, 2-A, 3-A, 4-A, 5-A, 6-D, 7-A, 8-A, 9-A, 10-A, 11-A, 12-A, 13-A, 14-A, 15-A, 16-A, 17-A, 18-A, 19-A, 20-A, 21-A, 22-A, 23-A, 24-A, 25-A, 26-B, 27-C, 28-C, 29-C, 30-D.

Answer-Audit: Important Concept Traps

Do not confuse zero potential with zero electric field.
A conductor in electrostatic equilibrium is equipotential, but its potential need not be zero.
Series capacitors have equal charge magnitude, not generally equal voltage.
Parallel capacitors have equal voltage, not generally equal charge.
Battery-connected means V is fixed by the ideal battery.
Isolated means Q remains fixed.
For a fully inserted dielectric, C increases by the factor K.
The effect on energy depends on whether Q or V is fixed.
Always judge the Assertion and Reason independently before testing the explanatory relationship.

Chapter 2 Resource Path

Electrostatic Potential and Capacitance — Chapter Hub
Complete Notes
Important Questions with Answers
MCQs with Answers
Numericals with Step-by-Step Solutions
Case-Based Questions
This page: Assertion–Reason Questions

Official Curriculum & Exam References

CBSE Class XII Physics Curriculum 2026–27

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

Next step: After Assertion–Reason practice, revise the chapter formula sheet and then attempt the chapter test under timed conditions.

Find a Study Resource

Electrostatic Potential and Capacitance Class 12 Physics Assertion Reason 2026-27

Electrostatic Potential and Capacitance Class 12 Physics Assertion–Reason Questions

How to Answer Assertion–Reason Questions

Assertion–Reason Practice Set

1. Electric potential is a scalar quantity.

2. The potential due to a point charge varies inversely with distance from the charge.

3. Electric potential can be zero at a point where electric field is non-zero.

4. No work is done by the electrostatic field when a charge is moved along an equipotential surface.

5. Electric field is perpendicular to an equipotential surface.

6. The electric potential at the midpoint of two equal positive charges is zero.

7. The electrostatic potential energy of two like charges is positive when the reference at infinity is zero.

8. The potential energy of two unlike point charges is negative when the reference at infinity is zero.

9. A conductor in electrostatic equilibrium is an equipotential body.

10. The electric field inside the conducting material of a conductor is zero in electrostatic equilibrium.

11. Excess charge on an isolated conductor in electrostatic equilibrium resides on its surface.

12. Capacitance is a property determined by the geometry of the capacitor and the dielectric medium between its conductors.

13. A capacitor can have a larger capacitance without storing more charge.

14. Two capacitors connected in parallel have the same potential difference.

15. Two capacitors connected in series carry the same magnitude of charge.

16. The equivalent capacitance of capacitors connected in parallel is greater than each individual capacitance.

17. The equivalent capacitance of two positive capacitors connected in series is smaller than either capacitor.

18. Inserting a dielectric completely between the plates of a capacitor increases its capacitance.

19. When a dielectric is inserted into an isolated charged capacitor, its charge remains constant.

20. When a dielectric is inserted fully into a capacitor that remains connected to an ideal battery, the potential difference remains constant.

21. For an isolated capacitor, inserting a dielectric fully between its plates decreases the potential difference.

22. For an isolated capacitor, inserting a dielectric fully between its plates decreases the stored energy.

23. For a capacitor connected to an ideal battery, inserting a dielectric fully between the plates increases the stored energy.

24. Doubling the plate separation of a parallel-plate capacitor doubles its capacitance.

25. If the plate area of a parallel-plate capacitor is doubled while all other factors remain unchanged, its capacitance doubles.

26. The energy stored in a capacitor can be written as U = ½CV².

27. The voltage across capacitors in a parallel combination is the same.

28. The charge on capacitors in a series combination is the same in magnitude.

29. Electric potential is zero at every point inside a charged conducting shell.

30. The electric field is always zero at every point where electric potential is zero.

Answer Key

Answer-Audit: Important Concept Traps

Chapter 2 Resource Path

Official Curriculum & Exam References

Comments

Post a Comment

26. The energy stored in a capacitor can be written as `U = ½CV²`.