A Machine that converts electrical energy into mechanical energy. One type of electric
motor consists of a conducting loop mounted on a nonconducting shaft. Current
fed to Carbon brushes enters the loop through two slip rings. A Magnetic Field around the loop, supplied by an iron-core Field magnet, causes the loop to turn when current flows through it. In an Alternating Current (AC) motor, the current flowing in the loop is synchronized (see Synchronous Operation of a Machine) to reverse direction at the moment when the plane of the loop is Perpendicular to the magnetic Field and there is no magnetic force exerted on the loop. Because the Momentum of the loop carries it around until the current is again supplied, continuous Motion results. In AC Induction, the current passing through the loop does not come from external sources but
is induced as the loop passes through a magnetic field. In direct-current (DC)
motors, a split-ring commutator switches the direction of the current each
half rotation to maintain the shaft's direction of motion. In a brushless DC
motor, the rotating portion contains a permanent magnet and the conducting coil of
wire (see Conductor) is stationary. In any motor, the stationary parts constitute the stator, and
the assembly that turns is called the rotor, or armature.
See Also: Locked Rotor Current