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AC generator
Intermediate
A rotating coil produces sinusoidal emf.
ε = NBAω sinωtA coil rotating at ω in a field produces ε = NBAω sin ωt. Power stations rotate coils with turbines.
N = 100, A = 0.05 m², B = 0.5 T, 50 Hz: peak 785 V.
Peak EMF scales with speed.
In more detail
An AC generator rotates a coil in a magnetic field, changing the flux through it and producing a sinusoidal emf. The frequency is set by the rotation rate.
Real-world uses
- Power stations use generators driven by turbines.
- Bicycle dynamos use a rotating magnet to generate electricity.
- Power stations use large rotating coils in generators to produce the sinusoidal voltage fed to the grid.
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Frequently asked questions
Why does the output alternate?
Because the flux changes direction as the coil rotates, reversing the induced emf.
What sets the frequency?
The rotation speed and the number of poles.
How does a generator make AC?
As the coil rotates, the flux through it changes sinusoidally, which induces a sinusoidal emf.
Related topics in Magnetism & Induction
Mutual inductance · Transformer · Transformer losses · Dynamo and alternator · Back emf in a motor · LR circuit growth and decay