A molecule with a dipole moment `p` is placed in an electric field of strength `E`. Initially the dipole is aligned parallel to the field. If the dipole is to be rotated to be anti-parallel to the field, the work required to be done by an external agency is

Options

A. `-2pE`
B. `-pE`
C. `pE`
D. `2pE`

Answer

D

Explanation

`W = pE (1 - cos theta)` here `theta = 180^(@)`
`:. W = pE (1- cos 108^(@)) = pE [1 - (-1)] = 2pE`