The commutator is a cylindrically shaped assembly that is fastened to the motor shaft and is considered part of the armature assembly. It consists of segments of “bars” that are electrically connected to two ends of one (or more) armature coils. Current is from the power supply through the brushes, to the commutator and hence through the armature coils. The arrangement of commutator segments is such that the magnetic polarity of each coil changes as the armature rotates.