What does it mean when the direction of the magnetic field through the coil reverses? Why would it reverse and what is the point of that??
Spinning around It is not practical to generate large amounts of electricity by passing a magnet in and out of a coil of wire. Instead, generators induce a current by spinning a coil of wire inside a magnetic field, or by spinning a magnet inside a coil of wire. As this happens, a potential difference is produced between the ends of the coil, which causes a current to flow. One simple example of a generator is the bicycle dynamo. The dynamo has a wheel that touches the back tyre. As the bicycle moves, the wheel turns a magnet inside a coil. This induces enough electricity to run the bicycle's lights.