Question

Derive the expression for potential energy due to electric dipole placed in an electric field

Answer 1

Suppose an electric dipole of dipole moment p is placed along a direction, making an angle θwith the direction of an external uniform electric field E. Then, the torque acting on the dipole is given by

If the dipole is rotated through an infinitesimally small angle dθ, against the torque acting on it, then the small work done is given by

If the dipole is oriented, making an angle θ1 to θ2 with the electric filed, then the total work done is given by

W = pE (cos θ1 − cos θ2)

This work done is stored in the dipole in the form of its potential energy.

∴U = pE (cos 90° − cos θ)

U = − pE cos θ

U = −