Question

A point charge placed at any point on the axis of an electric dipole at some large distance experiences a force F. The force acting on the point charge when it’s distance from the dipole is doubled is

• A. F
• B. $\frac{F}{2}$
• C. $\frac{F}{4}$
• D. $\frac{F}{8}$

Answer 1

Answer: (D)

$\frac{F}{8}$

Answer 2

Force acting on a point charge in dipole field varies as $F \propto \frac{1}{r^{3}}$ where r is the distance of point charge from the centre of dipole. Hence if r makes double so new force $F' = \frac{F}{8}$.