How electricity is generated

Diagram of a turbine generator - Spinning rotor turning coiled copper wir inside stationary magnets to generate electricity.

Turbine generator

Source: Adapted from Energy for Keeps (public domain)

A generator can be broadly defined as a device that converts a form of energy into electricity. Nearly all of the electricity consumers use is produced by generators that convert kinetic (mechanical) energy into electrical energy. Generators operate because of the relationship between magnetism and electricity. In 1831, scientist Michael Faraday discovered that when a magnet is moved inside a coil of wire, an electric current flows in the wire.

The most widely used method of producing electricity uses generators with an electromagnet—a magnet produced by electricity—not a traditional magnet. The generator has a series of insulated coils of wire that form a stationary cylinder. This cylinder surrounds a rotary electromagnetic shaft. When the electromagnetic shaft rotates, it induces a small electric current in each section of the wire coil. Each section of the wire coil becomes a small, separate electric conductor. The small currents of the individual sections are added together to form one large current. This current is the electricity that is transmitted from generators to consumers.

An electric power plant uses a turbine or other similar machine to drive these types of generators. There are steam turbines, gas combustion turbines, water turbines, and wind turbines.

Steam turbines using biomass, coal, geothermal energy, natural gas, nuclear energy, and solar thermal energy produce about 70% of the electricity used in the United States. These power plants are about 35% efficient. That means that for every 100 units of primary heat energy that go into a power plant, only 35 units are converted to useable electrical energy.

Other types of devices that generate or produce electricity include electrochemical batteries, fuel cells, solar photovoltaic cells, and thermoelectric generators.