The electric motor and magnetic-field problems

An electric motor converts electrical energy into mechanical energy; its operation rests on the Ampère force acting on a current-carrying loop in a magnetic field. The fixed part is the stator (it produces the magnetic field) and the rotating part is the rotor (the wound armature). If the current direction in the loop did not change when the rotor reached a half-turn, the forces would turn it back. So the commutator (two half-rings) reverses the current every half-turn, and the brushes pass the current to the rotating rotor. As a result the forces keep turning the rotor in one direction. Motors are used in trams, electric trains, drills and fans; their efficiency is much higher than that of heat engines. Keep hands, hair and clothes away from the rotating parts of a working motor, and do not open devices connected to the mains.