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` & 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`