Transformers are electrical devices that are used to transfer electrical energy from one circuit to another through electromagnetic induction. They are used to change the voltage level of an electrical signal, making it suitable for use in different applications. They consist of two or more coils of wire that are wound around a common magnetic core. When an alternating current (AC) voltage is applied to one of the coils, it generates a magnetic field that induces an AC voltage in the other coil(s). By changing the number of turns in each coil, transformers can change the voltage level of an electrical signal.