Question

A given charge is situated at a certain distance from an electric dipole in the end on position, experience a force F. If the distance of the charge is doubled, the force acting on the charge will be

• A. 2F
• B. F/2
• C. F/4
• D. F/8

Answer 1

Answer: (D)

F/8

Answer 2

We know that for end - on position

$E_{\text{end on}} = \frac{1}{4\pi\varepsilon_{0}}\text{ x }\frac{\text{2p}}{r^{3}}$

∴ $F = \frac{1}{4\pi\varepsilon_{0}} \times \frac{2pq}{r^{3}}$

when the distance is doubled, then

$\text{F' } = \ \frac{1}{4\pi\varepsilon_{0}} \times \frac{2pq}{(2r)^{3}}$ = $\frac{1}{8}\left\lbrack \frac{1}{4\pi\varepsilon_{0}} \times \frac{2pq}{r^{3}} \right\rbrack = \frac{F}{8}$