An electric dipole is kept on the axis of a uniformly charged ring at distance from the centre of the ring. The direction of the dipole moment is along the axis. The dipole moment is P, charge of the ring is Q and radius of the ring is R. The force on the dipole is

Answer

D

Explanation

Force on a dipole `F=p(del E)/(del x)`
At `x=R/sqrt(2), (del E)/(del x)=0`, so `F=0`