An electric motor is a coil of insulated wire in a magnetic field with a direct current passing through it. The forces on each edge of the coil are in opposite directions and make the coil spin continuously. This is known as the motor effect. A split-ring commutator attached to the coil allows the coil to spin whilst making contact with two graphite brushes supplying the current. This means that the current through the coil changes direction with each 180° turn and the two forces are always acting in the same direction.