Static electrical machine that transforms electrical power from one electrical circuit to another on the principle of mutual induction. Basically, the transformer consists of two coils, known as the primary winding and the secondary winding. These are not connected electrically but are magnetically linked to each other. When the varying current is applied to the primary winding (e.g., alternating current), it generates a changing magnetic field. The transformer core provides a path for the magnetic flux to reach the secondary winding. According to Faraday’s law of electromagnetic induction, current is induced in the secondary winding. The voltage can be decreased or increased in the transformer without changing the frequency. In tokamaks, the transformer principle is used to induce an electric current in the plasma. The plasma acts as the secondary winding of the transformer.