Question

For what orientation does an electric dipole experiences a zero torque but non-zero force in a non-uniform electric field?

Answer 1

When dipole moment 'p' is parallel or antiparallel to electric field 'E' , the net torque is zero, but there is a force on the dipole E which is not uniform. It is seen that when p is parallel to E, dipole has a net force in the direction of increasing field and when p is antiparallel to E, the net force on dipole is in the direction of decreasing field.