# Tag Info

The important thing here is that a magnetic dipole, like a permanent magnetic or induced magnetism in ferrous material, produces a nonuniform field. The potential energy of a magnetic dipole $\vec\mu$ in a magnetic field $\vec B$ is $$U = -\nabla( \vec \mu \cdot \vec B).$$ Most frequently (as in anna v's answer) this is used to explain the torque which ...