Transformers

In electric power distribution systems it is important to convert a small AC voltage to a larger one or vice versa. The device used for these conversions is the transformer. Transformers are found in many electronic devices nowadays, such as television and mobile phone.

Principle of a Transformer

A transformer consists of two coils of wire known as the primary and secondary coils which are not connected directly to each other. The two coils are usually wound separately on a soft iron core. The purpose of the soft iron core is to provide a magnetic field linkage in the secondary coil.

When an alternating current flows in the primary coil, an induced magnetic field is produced in the soft iron core. This constantly changes the magnetic flux linkage in the secondary soil. Therefore, an alternating e.m.f induced across it.

A voltage is generated across the secondary soil only when there is a change in the flux linkage through the secondary coil. Thus the current in the primary coil must keep on changing as in the case of an alternating current. For this reason, a transformer can only function with an AC input.

The frequency of the secondary voltage is the same as that of the primary voltage.  The magnitude of the secondary voltage, however, depends on the ration of the number of turns of the primary and secondary coils.

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