A
commutator is a moving part of a rotary
electrical switch in certain types of
electric motors and
electrical generators that periodically reverses the
current direction between the rotor and the external circuit. It consists of a cylinder composed of multiple metal contact segments on the rotating
armature of the machine. The commutator is one component of a motor; there are also two or more stationary
electrical contacts called "
brushes" made of a soft conductor like
carbon that press against the commutator, making sliding contact with successive segments of the commutator as it rotates. The windings (coils of wire) on the
armature are connected to the commutator segments.