Question

Given below are two statements: one is labelled as Assertion A and the other is labelled as Reason R.
Assertion A : The potential (V) at any axial point, at 2 m distance(r) from the centre of the dipole of dipole moment vector $\vec{P}$ of magnitude, 4 × 10-6 C m, is ± 9 × 103 V.
(Take $\frac{1}{4\pi\epsilon_0}=9\times10^9$ SI units)
Reason R : $V=±\frac{2P}{4\pi \epsilon_0r^2}$, where r is the distance of any axial point, situated at 2 m from the centre of the dipole.
In the light of the above statements, choose the correct answer from the options given below :

• A. Both A and R are true and R is the correct explanation of A.
• B. Both A and R are true and R is NOT the correct explanation of A.
• C. A is true but R is false.
• D. A is false but R is true.

Answer 1

Answer: (C)

A is true but R is false.

Answer 2

Substitute values into $V = \pm \frac{2P}{4\pi\epsilon_0 r^2}$:

$V = \pm \frac{2(4 \times 10^{-6})}{4\pi(9 \times 10^9)(2)^2} = \pm 9 \times 10^3 \, V$.

Assertion A is true, but Reason R fails to consider directionality.