Nguyên văn bởi Gú gồ

There are magnetic fields around a magnet that form closed loops. Although you can't see these fields there existence can be observed by taking two magnets and seeing that they pull themselves together when opposite poles are placed next to each other or push themselves apart if like poles are brought together.
If a wire is simply sitting next to a magnet then no voltage potential will be created in the wire. For a voltage potential to be created the wire (or the magnet) must physically be moving. Specifically it must be moving as a function of time. As long as the wire moves through the field around the magnet a voltage potential will be created. This process is described by Faraday's law of induction and is the basis for all modern generators.