Transformer is a device that increases or decreases the voltage of alternating current. Alternating current is electric current that regularly reverses its direction. Transformers provide a simple, inexpensive way to change such voltage. They enable electric power companies to transmit alternating current easily and efficiently. Transformers also ensure the proper voltage for the circuits of home appliances, lights, industrial machinery, and other electric equipment.
Most transformers consist of two coils of insulated wire.
One coil, known as the primary winding, is connected to the source of the voltage that is to be changed. This voltage is the input voltage of the transformer. The other coil, called the secondary winding, supplies the output voltage to the desired circuit. In most transformers, the primary and secondary windings are wound around a hollow core made of thin iron or steel sheets. Most cores have the shape of a ring or a square.