A transformer is a device that uses the principle of electromagnetic induction to change AC voltage. Its main components are the primary coil, the secondary coil, and the iron core (magnetic core). In electrical equipment and wireless circuits, it is often used to increase or decrease voltage, match impedance, and provide safety isolation. In a generator, whether the coil moves through a magnetic field or the magnetic field moves through a fixed coil, an electric potential can be induced in the coil. In both cases, the value of the magnetic flux remains unchanged, but the amount of magnetic flux interlinked with the coil changes. This is the principle of mutual induction. A transformer is a device that uses electromagnetic mutual induction to transform voltage, current, and impedance.