Question

An electric dipole has the magnitude of its charge as $q$ and its dipole moment is $p$. It is placed in a uniform electric field $E$. If its dipole moment is along the direction of the field, the net force acting on it and its potential energy are respectively

• A. $2qE$ and minimum
• B. $qE$ and $pE$
• C. Zero and minimum
• D. $qE$ and maximum

Answer 1

The correct option is C Zero and minimum

As shown in figure, the dipole is placed in uniform electric field in the direction of $\overrightarrow{E}$.


The net force on dipole is

$F_{net}=F_{q^{+}}+F_{q^{-}}$

$\Rightarrow F_{net}=qE-qE=0$

The angle between $\overrightarrow{p}$ and $\overrightarrow{E}$ is $0^{\circ }$. So, potential energy is given as

$U=-\overrightarrow{p}.\overrightarrow{E}=-pE\cos 0^{\circ }$

$\Rightarrow U=-pE$

It repents the maximum negative potential energy of dipole.

$\therefore$ $U$ is minimum.

Hence, option $\left(c\right)$ is correct.