Alternator: Coil with AC commutator rotates between magnets.

Alternator: Coil with AC commutator rotates between magnets. This is a simple alternator illustrating the principle that a changing magnetic field cutting across a loop of wire induces an electric current. In this case, the magnetic field is produced by two strong permanent bar magnets mounted in line with each other, on opposite sides of the wire coil; close to the perimeter of the coil. The coil of wire is rotated in this magnetic field, generating an emf. The crank-handle/pulley system is on the back of the apparatus, not visible in this drawing. The 'slip-ring' commutator causes the output of the alternator to be A.C. current in the milliamp range. For example, crank the handle clockwise or counterclockwise, and the current will go from 0 to +.5 ma to 0 to -.5 ma to 0, etc.