Question

The distance between the two charges $+q$ and $-q$ of a dipole is $r$. On the axial line at a distance $d$ from the centre of dipole, the intensity is proportional to

• A. $\frac{q}{d^2}$
• B. $\frac{qr}{d^2}$
• C. $\frac{q}{d^3}$
• D. $\frac{qr}{d^3}$

Answer 1

The correct option is D $\frac{qr}{d^3}$

Magnitude of intensity of the electric field on the axial line is
$E=\frac{1}{4\pi {\epsilon }_0}.\frac{2p}{d^3}$
Here $p$ is dipole moment , $p=qr$

$E=\frac{1}{4\pi {\epsilon }_0}.\frac{2\left(qr\right)}{d^3};$
$\therefore E\propto \frac{qr}{d^3}$