In electrical equipment and wireless circuits, transformers are often used for boosting, impedance matching, safety isolation and so on. In the generator, whether the coil moves through a magnetic field or a fixed coil, an electric potential can be induced in the coil. In both cases, the value of magnetic flux remains the same, but the amount of magnetic flux in the chain intersecting with the coil changes, which is the principle of mutual inductance. Transformer is a device that uses electromagnetic mutual inductance to transform voltage, current and impedance.