The ammonia molecule (NH3) has a dipole moment of 5.0 X 10-30 C • m. Ammonia molecules in the gas phase are placed in a uniform electric field E with magnitude 1.6 X 106 N/c.
(a) What is the change in electric potential energy when the dipole moment of a molecule changes its orientation with respect to E from parallel to perpendicular?
(b) At what absolute temperature T is the average translational kinetic energy 3/2 kT of a molecule equal to the change in potential energy calculated in part (a)? (Note: Above this temperature, thermal agitation prevents the dipoles from aligning with the electric field.)