大象传媒

Generators

Cars use a type of a.c. generator, called an alternator, to keep the battery charged and to run the electrical system while the engine is working.

A dynamo is another type of generator sometimes found on the back wheel of a bicycle to run the lights.

Both convert to electrical energy when a coil of wire rotates inside a magnet

A simple generator

The diagram shows a simple generator.

Current flows in external circuit. Brushes continuous contact between external circuit, slip rings. Slip rings connected to coil. Current induced in rotating coil. The coil rotated in magnetic field.
Figure caption,
A simple a.c. generator

The size of the induced voltage, and hence induced current, can be increased by:

  • increasing the speed of rotation of the coil;
  • using a stronger magnet;
  • increasing the number of turns on the coil.

Large scale a.c. generators in power stations are used to generate electricity.

The coil of these generators rotates 50 times a second and that is why our mains supply has a frequency of 50 Hz.

Northern Ireland has three fossil fuel power station:

  • Ballylumford, near Larne 鈥 natural gas;
  • Kilroot, near Carrickfergus 鈥 coal and oil;
  • Coolkeeragh, at Maydown, Londonderry 鈥 natural gas.

Recently, it has been reported that Kilroot is to be replaced by a new, modern gas-fired power station.