Question

An electric dipole of length $4cm$, when placed with its axis making an angle of 60° with a uniform electric field, experiences a torque of $4\sqrt{3}$ Nm. Calculate the potential energy of the dipole, if it has charge $\pm 8nC$.

Answer 1

As $\tau =pE\sin \theta$

$\therefore =43pE\sin \theta$ [1]

$\Rightarrow pE\times \frac{\sqrt{3}}{2}=4\sqrt{3}$

$\Rightarrow pE=8$

Potential energy of dipole,

$U=–pE\cos \theta$ [1]

$U=–pE\cos {60}^{\circ }$

$U=–4J$.