<P> A commutator is 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 . Two or more electrical contacts called "brushes" made of a soft conductive material like carbon 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 . </P> <P> Commutators are used in direct current (DC) machines: dynamos (DC generators) and many DC motors as well as universal motors . In a motor the commutator applies electric current to the windings . By reversing the current direction in the rotating windings each half turn, a steady rotating force (torque) is produced . In a generator the commutator picks off the current generated in the windings, reversing the direction of the current with each half turn, serving as a mechanical rectifier to convert the alternating current from the windings to unidirectional direct current in the external load circuit . The first direct current commutator - type machine, the dynamo, was built by Hippolyte Pixii in 1832, based on a suggestion by André - Marie Ampère . </P>

What is the function of commutator in motor
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