A NONSTANDARD EXPRESSION FOR THE FORCE AND TORQUE ON A MAGNETIC DIPOLE

A new expression for the force and torque on a magnetic dipole, with a magnetic moment changing with time and in the presence of time-varying electromagnetic fields produced by a charge distribution q, is derived. The force, which has relevance in the Aharonov-Bohm and Aharonov-Casher effects, is calculated for both conducting and non-conducting magnetic dipoles making use of the general stress tensor which includes the internal mechanical stresses of the dipole. The role played by the action and reaction principle in the interaction between a magnetic dipole and a charge in relative motion is also investigated.