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Basics of Electricity Generation

  • Electricity comes from the movement of electrons through a circuit

  • The connection between electricity and magnetism, discovered in the 19th century, allows us to generate electrical flow by moving magnets

  • Generators convert mechanical energy to alternating current electrical energy

What is electricity?

Electricity is the movement of charged particles such as electrons. This electron motion is sometimes referred to as a “secondary energy source,” since the electrical energy is produced by the conversion of a different primary energy source. Electricity is flexible, easy to use, and will never run out, because electrons themselves are never consumed. Because electricity is a flow of electrons, it must be used immediately once generated, or converted to a different form of energy to be stored.

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How do we generate electricity?

Electricity has always existed all around us - consider lightning, or static electricity from rubbing a balloon on a sweater. But it wasn’t until the late 18th century that scientists really began to understand what electricity was or how we could harness and use its power. They identified two essential ingredients to make electricity useful: (1) something to get electrons moving and

(2) something to direct electron flow in a particular direction.

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Generators - using magnets to move electrons:  

In the mid-19th century, Michael Faraday made the first generator when he discovered that a magnet moving through a coil of copper wire generated an electric current.

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Source.

The basic principle of Faraday’s first generator is still how generators work today. A turbine starts an electric current by either rotating a large magnet through a coil of wires, or rotating a coil of wires through a magnet. 

 

The mechanical energy that makes the turbine rotate can come from a variety of different sources. In direct systems, flows like wind and water can be used to physically rotate the magnet or coil, as you can see in a wind turbine or a hydroelectric turbine.


Electric power plants often use indirect energy sources to generate electricity. Energy from a primary source such as a fossil fuel (oil, coal, gas) or a fission reaction (in the case of nuclear) is used to heat water into steam. The motion of the steam rising powers the mechanical rotation of the turbine, generating the electrical current.

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Figure adapted and modified from Best Practice Energy.

Types of electricity

Most generators used in large scale power plants generate electricity in the form of alternating current (AC). In AC, the electric current switches back and forth rather than flowing in one direction. For more information about AC versus DC (direct current), check out our electricity transmission module.

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Questions for deeper thinking

  • Qualitatively, how might the efficiency compare between a system that directly converts kinetic energy to electrical energy (water turbine, wind turbine) to one that needs to burn fuels to generate steam first (fossil fuels and steam turbines)? Consider the inherent energy losses from each energy conversion step.

Sources and further reading

Page last updated: August 31, 2022​

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