Derive the expression for the torque acting on an electric dipole, when it is held in a uniform electric field. Identify the orientation of the dipole in the electric field, in which it attains a stable equilibrium.
Let us consider, the force on either charge be ;-
we know, the magnitude of torque is given as ;
either force perpendicular distance between them
therefore,
Such that, (From the definition of dipole moment)