(i) Obtaining of the expression for torque experienced by an electric dipole (ii) Effect of non-uniform electric field (i) Force on $+q, \overset{\rightarrow}{F}=q \overset{\rightarrow}{E}$ Force on $-q, \;\; \overset{\rightarrow}{F}=-q \overset{\rightarrow}{E}$ Magnitude of torque $\tau\;=q E \times 2 a \sin\;\theta$ $\;=2 q a E \sin\;\theta$ $\overset{\rightarrow}{\tau}\;=\overset{\rightarrow}{p}\times \overset{\rightarrow}{E}$ (ii) If the electric field is non uniform, the dipole experiences a translatory force as well as a torque.