A motor has a stator having a stator core and field windings. The brush gear includes a plurality of brushes, a rotor including a shaft, a rotor core fixed to the shaft, a commutator fixed to the shaft adjacent the rotor core and rotor windings wound about teeth of the rotor core and connected to the commutator. The stator core has a yoke, 2P primary poles about which the field windings are wound, and 2P auxiliary poles. A control device controls the electrical connection of the field windings and the brushes so that 2P or 4P magnetic poles are selectively formed on the stator core when the field windings are electrified. P is an integer equal to or greater than 1.