Physics · Electrostatics · chapter 2 of 14

Class 12 Physics Chapter 2: Electrostatic Potential and Capacitance Assertion-reason questions with answers

2 assertion-reason questions on Electrostatic Potential and Capacitance, each with its answer and the reason, written from the NCERT chapter. For the CBSE board, JEE Main and NEET, which are set from the same NCERT chapter. Open a question's solution to check your working; then take the free test to find your next chapter. Each question gives an Assertion (A) and a Reason (R); choose how they stand to each other.

Question 1
Assertion (A): No work is done by the electric field when a test charge moves from one point to another on the same equipotential surface. Reason (R): The potential difference between any two points on an equipotential surface is zero, and the work done by the field is W = −qΔV.
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Answer: (a) Both A and R are true, and R is the correct explanation of A.

Both are true, and R is the reason: the work done by the field in moving q through a potential difference ΔV is −qΔV, and on an equipotential surface ΔV = 0, so W = 0.

Question 2
Assertion (A): The electrostatic potential at every point of the equatorial plane of a dipole is zero. Reason (R): At large distances the potential of a dipole falls off as 1/r², not as 1/r.
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Answer: (b) Both A and R are true, but R is not the correct explanation of A.

A is true: in the equatorial plane θ = π/2, so V = p cos θ/(4πε₀r²) = 0. R is true too, but the 1/r² fall-off does not explain why V is zero on that plane; the cos θ factor does.

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