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A battery converts chemical energy into electricity, and a solar cell produces electricity from the sun's energy, but if you want to produce electricity from mechanical energy, you need an induction generator. These generators can be small enough to power a crank-style flashlight or large enough to energize entire cities, but all work on the principle of electromagnetic induction, discovered by Michael Faraday, the 19th-century English physicist and inventor. Today, induction generators running on a variety of fuels supply electricity for most of the world's population.
Faraday's induction experiment is probably one of the most important in physics, and it was a relatively simple one. He coiled a length of conductive wire around a circular core and connected the wire to a meter. He found that moving a magnet through the center of the circle caused current to flow in the wire. The current stopped when he stopped moving the magnet, and it flowed in the opposite direction when he reversed the direction of the magnet. He later formulated the law of electromagnetic induction, now known as Faraday's Law, which related the strength of the current to the magnitude of the change of the magnetic field, also known as magnetic flux. The strength of the magnet, the number of coils around the core and the characteristics of the conducting wire all influence calculations for real-world generators.
Whether located inside a household utility generator, your car or a nuclear power plant, generators generally incorporate the same features. They include a rotor with a hollow core that rotates around a stator. The stator is typically a powerful magnet, while the coils that carry electricity are wound around the rotor. In some generators, the coils are wound around the stator and the rotor is magnetized. It doesn't matter. Either way, electricity will flow.
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