The transformer is mainly composed of a coil (also called a winding) and a core.
The transformer is made according to the principle of electromagnetic induction. When the magnetic flux passing through the coil changes, an induced electromotive force is generated at both ends of the coil. The level of the induced electromotive force is proportional to the number of turns of the coil.
A typical transformer typically has two coils, one primary, connected to the power supply, and the other secondary to the load. The two coils are placed on the same closed core. As shown.
The iron core constitutes the magnetic circuit of the transformer. The primary coil is connected to an alternating current, and an electric current generates an alternating magnetic field in the iron core. This magnetic field passes through the secondary coil that is placed over the iron core, and an induced electromotive force is generated at both ends of the secondary coil. The ratio of this electromotive force to the supply voltage is equal to the turns ratio of the two coils.