Question

An electric dipole is held in a uniform electric field.
(i) Show that the net force acting on it is zero.
(ii) The dipole is aligned parallel to the field. Find the work done in rotating it through the angle fo `180^(@)`.

Answer 1

(i) Force acting on charge - q and +q of a dipole is equal and in opposite direction. So, net force is zero but their line of action may be different so the dipole may experience a torque.
(ii) `W=pE(cos q2- cos q1)`
`=pE (cos 180^(@)-cos 0^(@))=pE(-1-1)=-2pE`