Question

If the force exerted by an electric dipole on a charge $q$ at a distance of $1 \,m$ is $F$, the force at a point $2$ m away in the same direction will be

• A. $\frac{F}{2}$
• B. $\frac{F}{4}$
• C. $\frac{F}{6}$
• D. $\frac{F}{8}$

Answer 1

Answer: (D)

Force exerted by an electric dipole on a charge is inversely proportional to the cube of distance of the charge from the centre of the dipole
$F \propto \frac{1}{r^{3}}$
$\therefore \frac{F}{F^{'}}=\left(\frac{r^{'}}{r}\right)^{3}$
$\frac{F}{F^{'}}=\left(\frac{2}{1}\right)^{3}$
$F^{'}=\frac{F}{8}$