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A varying electrical current in the coil on the left produces a fluctuating magnetic field. This loops through the coil on the right, inducing an electrical current. Image by Ponor, CC BY-SA 4.0 via Wikimedia Commons. |
Two principles, discovered in the early 19th century on which motors, generators and transformers work.
Electromagnetic Induction
Move
a conductor (e.g. a piece of wire) in a magnetic field (produced by a
magnet), or move the field and keep the conductor stationary or thirdly,
vary the strength of the field. The result is that a current is induced
in the conductor. This is how all electrical generators and
transformers work, electricity being induced or generated in coils of
wire as a magnetic field varies in strength. It's the main reason too
why we use AC electricity for distribution.
Force on a Conductor in a Magnetic Field
Pass
a current through a conductor placed in a magnetic field. The conductor
experiences a force which tends to push it. This is the principle on
which electric motors work.
Several
scientists in the early 19th century made fundamental discoveries about
the nature of electric currents and magnetic fields. Two of these were
the Danish physicist Hans Christian Ørsted and the English scientist
Michael Faraday. Faraday's apparatus including a transformer and motor
can be seen in the Faraday Museum at the home of the Royal Institution
in London.