The potential energy of an electric dipole in a uniform electric field is u . The magnitude of the torque acting on the dipole due to the field is N . Then
(a) u is minimum and N is zero when the dipole is parallel to the field
(b) u is zero and N is zero when the dipole is perpendicular to the field
(c) u is minimum and N is maximum when the dipole is perpendicular to the field
(d) u is minimum and N is zero when the dipole is anti-parallel to the field
