The External Electric Field of a Rotating Magnet.

The electromagnetic fields outside rigidly rotating magnets in vacuum are computed in two cases: for a nonconducting magnet with dielectric constant unity the electric and magnetic fields are given exactly in terms of retarded potentials; for a conducting magnet the electric and magnetic fields are computed in the region of space where the displacement current can be neglected. In the former case the rotation of the magnet has no effect unless its stationary magnetic field is axially asymmetric. One example of the latter case is that a uniformly magnetized conducting sphere rotating about its axis of magnetization produces an external electric quadrupole field. These results contradict 's results for the same problem (1950, see p. 8) but agree with the experimental results he cites in favor of his theory.