Transformer

A transformer is a device used to convert low a.c. voltage into high a.c. voltage and vice versa. It is of two types: -

1. Step-up transformer
2. Step-down transformer

A step-up transformer converts low a.c. voltage into high a.c voltage and step-down transformer converts high a.c. voltage into low a.c voltage. The instrument is based on the principle of mutual induction.

Structure: It consists of a rectangular soft iron core made up of laminated sheets. There are two coils which are not connected to one another in any way. These coils are wound on the iron core. One of the coils may be connected to a source of a.c. This coil is called primary coil and the other is called secondary coil.

The e.m.f. of a.c. source applied across the primary coil is called input voltage and e.m.f. induced across the secondary coil is called output voltage.

Principle: When an alternating e.m.f. is applied to the primary coil, a changing current flowing in it produces an alternating magnetic flux in it. This causes to change the magnetic flux linked with the secondary coil. An alternating e.m.f. is then induced in the secondary coil. It is called principle of mutual induction on which transformers are based.

The formula showing the relation between the primary voltage and secondary voltage is as follows: -

Uses

1. Transformers are used in voltage regulators for computer, television, air conditioner, record player, etc.
2. It is used to transmit the alternating current over long distances.
3. It is used for doorbells, welding purpose and in electrical furnaces.
4. It can be used to prevent DC from passing from one circuit tothe other.
5. It can isolate two circuits electrically.