On the magnetic dipole energy expression of an arbitrary current distribution

Abstract

We show that the magnetic dipole energy term appearing in the expansion of the magnetic potential energy of a localized current distribution has the form $ U= + \bf{m} \cdot \bf{B}$ which is wrong by a sign from the well known $ - \bf{m} \cdot \bf{B}$ expression. Implication of this result in relation to the electric dipole energy $ - \bf{p} \cdot \bf{E}$, and the force and torque on the magnetic dipole based on this energy expression is also discussed.