Closeup of an electric motor from a vacuum cleaner, showing the commutator. This is a universal motor that runs on alternating current. The commutator is a rotary switch that supplies power to the rotor windings, reversing the direction of current with each half turn so the magnetic field of the winding exerts a steady torque to turn the rotor in one direction. Labeled parts: "(A)" commutator, "(B)" brush, "(C)" rotor (armature) winding, "(D)", stator (field) winding, "(E)" brush guide. Alteration to original image: changed labels of parts from German to letters.