Power stations generate electricity from burning fossil fuels.
The energy released from burning coal, oil, or gas is used to heat water and produce steam, which drives a turbine that spins a generator to generate electricity.

Inside the generator, a spinning coil of wire cuts through a permanent magnetic field, inducing an electromotive force (emf) in the coil. This coil of wire is part of a complete circuit and thus generates an electric current. As the orientation of the coil changes during rotation, the direction of the induced emf and, hence, the current change every half-turn, creating an alternating emf.

The coil spins at a constant angular velocity, causing the flux linkage to change continuously.

When the normal to the plane of the coil is parallel to the magnetic field lines, the magnetic flux linkage is a maximum as, and .

The graph below shows how the magnetic flux linkage changes against time starting at . When the normal is parallel to the field lines.

Using Faraday’s law, we can plot the corresponding induced emf against time graph directly below the magnetic flux graph, as the rate of change of magnetic flux linkage is proportional to the induced emf.

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Therefore, the gradient of the magnetic flux against time graph gives the emf induced.

The maximum emf, , induced in a rotating coil , from the equation we have seen before, , as the emf is a maximum when , which occurs at , when the normal is perpendicular to the field lines.

A dynamo is similar to an alternator, except it features a split-ring commutator. It needs this to ensure that a direct current is output.

As the coil rotates, it cuts the magnetic field lines, inducing an electromotive force (emf) that reverses every half-turn due to the changing orientation of the coil. One half of the split ring commutator is connected to each end of the coil so that every half turn, each half of the slip ring switches contacts, cancelling out the change in direction of the induced emf and thus current. This ensures that the current in the external circuit always flows in one direction.

Some bikes utilise this principle to run the lights while the wheels are in motion.