Question
(a) Derive an expression for the electric field E due to a dipole of length '2a' at a point at a distance r from the centre of a dipole on the axial line.
(b) Draw a graph of E versus r for r >> a.
(c) If this dipole was kept in a uniform external electric field E0, diagrammatically represent the position of the dipole in stable and unstable equilibrium and write the expressions for the torque acting on the dipole in both the cases.