Electrical generator

In electricity generation, an electric generator is a device that converts mechanical energy to electrical energy. The reverse conversion of electrical energy into mechanical energy is done by amotor; motors and generators have many similarities. A generator forces electrons in the windings to flow through the externalelectrical circuit. It is somewhat analogous to a water pump, which creates a flow of water but does not create the water inside. Thesource of mechanical energy may be a reciprocating or turbinesteam engine, water falling through a turbine or waterwheel, aninternal combustion engine, a wind turbine, a hand crank,compressed air or any other source of mechanical energy.

Historical developments

Before the connection between magnetism and electricity was discovered, electrostatic generatorswere invented that used electrostatic principles. These generated very high voltages and lowcurrents. They operated by using moving electrically charged belts, plates and disks to carry charge to a high potential electrode. The charge was generated using either of two mechanisms:

• Electrostatic induction
• The triboelectric effect, where the contact between two insulators leaves them charged.

Because of their inefficiency and the difficulty of insulating machines producing very high voltages, electrostatic generators had low power ratings and were never used for generation of commercially-significant quantities of electric power. The Wimshurst machine and Van de Graaff generator are examples of these machines that have survived.