A homopolar motor is a direct current electric motor with two magnetic
poles, the conductors of which always cut unidirectional lines of magnetic
flux by rotating a conductor around a fixed axis that is parallel to the
magnetic field. The resulting Electromotive Force is continuous in one
direction; the homopolar motor needs no commutator but still requires slip
rings. The name homopolar indicates that the electrical polarity of the
conductor and the magnetic field poles do not change (i.e., that it does not
require commutation).