A point $Q$ lies on the perpendicular bisector of an electrical dipole of dipole moment $p$. If the

Question

A point $Q$ lies on the perpendicular bisector of an electrical dipole of dipole moment $p$. If the distance of $Q$ from the dipole is $r$ (much larger than the size of the dipole), then the electric field at $Q$ is proportional to

Professor PC Thomas Classes · Answer

The electric field at a point on equatorial line (perpendicular bisector) of dipole at a distance $r$ is given by
$E=\frac{p}{4 \pi \varepsilon_{0}} \cdot \frac{1}{\left(r^{2}+a^{2}ight)^{3 / 2}}$ where $2 a=$ length of dipole
For $r \gg a$
$	herefore \quad E=\frac{p}{4 \pi \varepsilon_{0}} \cdot \frac{1}{r^{3}}$ i.e., $E \propto p$ and $E \propto r^{-3}$