Question

The relation between the intensity of the electric field of an electric dipole at a distance $r$ from its centre on its axis and the distance $r$ is

• A. $E\propto \frac{1}{r}$
• B. $E\propto \frac{1}{r^2}$
• C. $E\propto \frac{1}{r^4}$
• D. $E\propto \frac{1}{r^3}$

Answer 1

Answer: (D)

$E\propto \frac{1}{r^3}$

Electric field due to an electric dipole at axial point
$E_{axial}=\frac{2kpr}{(r^2-l^2{)}^2}$
If $r>>1$, then $E_a=\frac{1}{4\pi {ϵ}_0}\frac{2p}{r^3}\Rightarrow E\propto \frac{1}{r^3}$
(directed from $-q$ to $+q$).