Detailed Description of a DC Generator

A generator is the opposite of a motor; while a motor turns electrical energy into mechanical energy, a generator does exactly the reverse. Unlike alternating current generators, which produce current that periodically changes direction, a DC generator produces unidirectional current.

Features

• All direct current generators include at the minimum a rotating coil of wire; a split ring (with two breaks in it) that rotates together with the coil; two stationary metal brushes that transfer current from the rotating split ring to the external circuit and magnets that generate a magnetic field. The magnets may be permanent magnets or electromagnets. The combination of split ring and brushes is called a commutator.

Function

• As the coil of wire turns in the magnetic field, the magnetic flux (the total number of magnetic lines of force) passing through the loop of wire changes, because the angle between the coil and the magnetic field is always changing. In keeping with Faraday's Law, this change in magnetic field creates a voltage in the coil of wire and thereby generates electric current.

Considerations

• In an AC generator the EMF (electromotive force) if plotted as a function of time is a smooth wave-shaped graph (a sine wave), where the EMF is sometimes positive and sometimes negative. In a DC generator, the EMF rises from zero to max and falls back to zero, but never becomes negative. Some DC generators use more than one coil to smooth out this bumpy wave pattern and produce a more constant current.