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 $U=+\mathbf{m}\cdot \mathbf{B}$ which is wrong by a sign from the well known $-\mathbf{m}\cdot \mathbf{B}$ expression. Implication of this result in relation to the electric dipole energy $-\mathbf{p}\cdot \mathbf{E}$, and the force and torque on the magnetic dipole based on this energy expression is also discussed.