Suppose an external torque tttttext is
applied in such a manner that it just neutralises this
torque and rotates it in the plane of paper from angle q0
to angle q1 at an infinitesimal angular speed and without
angular acceleration The amount of work done by the
external torque will be given by
(
)
cos
cos
pE
θ
θ
0
1
=
−
(2 31)
This work is stored as the potential energy of the system We can
then associate potential energy U(q) with an inclination q  of the dipole