Question

An electric pole of dipole moment $\underset{p}{\to }$ is lying along uniform electric field $\underset{E}{\to }$. The work done in rotating the dipole by 90${}^{\circ }$ is:-

• A. $\sqrt{2}$ pE
• B. $\frac{pE}{2}$
• C. 2pE
• D. pE

Answer 1

The correct option is D pE

Work done in rotating a dipole from ${\theta }_1$ to ${\theta }_2$ is
$W$ = $pE(\cos {\theta }_1-\cos {\theta }_2)$
Here ${\theta }_1$ = $0^{\circ }$ and ${\theta }_2$ = ${90}^{\circ }$ therefore W = pE