An electric motor has a housing, a rotor rotatably installed in the housing, n permanent magnets with the same polarity fixed at an inner surface of the housing. The rotor is a wound armature having a plurality of teeth extending in a radial direction. The housing includes n inner projecting parts, the permanent magnets and the inner projecting parts being alternately arranged in a circumferential direction about the rotor. The magnets generate 2n magnetic circuits via the housing and the rotor, n being an integer greater than one. The size of at least a portion of a first air gap formed between the permanent magnets and the rotor is greater than the size of at least a portion of a second air gap formed between the inner projecting parts and the rotor.