When an electric dipole is placed in a uniform electric field making angle `theta` with electric field, it experiences a torque `tau`. Calculate the minimum work donein changing the orientation to `2 theta`.

Explanation

`tau` = pE sin`theta`
`rArr " pE" = (tau)/(sin theta)`
W = `Delta`U = -pE cos`theta_(2) + "pE"cos theta_(1)`
`rArr " W " = pE [ cos theta - cos 2 theta]" " (because theta_(1) = theta, theta_(2) = 2theta)`
`rArr " W " = (tau)/(sin theta) [ cos theta - cos 2 theta] `