An electric dipole of dipole moment $\vec p$ is rotated in an electric field of magnitude E from the most stable orientation to most unstable orientation. The work done in the process is:

2pE

The correct answer is Option (2) → 2pE

The potential energy (U) of a dipole is -

$U=-\vec p.\vec E=-pE\cos θ$

∴ Work done in rotating the dipole (W) is -

$W=U_{final}-U_{initial}$

$=pE(\cos 180°)-(-pE\cos 0°)$

$=pE+pE$

$=2pE$