Transformers

Transformers change the voltage of an alternating current (a.c.) electrical supply.

Step-up transformers increase the output voltage, while step-down transformers decrease it.

A step-up transformer has more coils of wire on the secondary coil than on the primary coil, while a step-down transformer has more coils of wire on the primary coil than on the secondary coil.

How Transformers Work

When an alternating current flows through the primary coil (input coil) of a transformer, it produces a changing magnetic field in the laminated soft iron core.

This changing magnetic field induces a potential difference (voltage) in the secondary coil (output coil).

Equations for Transformers

The ratio of the primary voltage to the secondary voltage is equal to the ratio of the number of turns on the primary coil to the number of turns on the secondary coil:

Vp/Vs = Np/Ns

Where:

Vp is the voltage applied to the primary coil
Vs is the voltage induced in the secondary coil
Np is the number of turns on the primary coil
Ns is the number of turns on the secondary coil

This equation can be used to calculate the transformer output voltage if the input voltage and number of turns on the primary and secondary coils are known.

Uses of Transformers

Transformers are widely used in power distribution systems to step-up the voltage for transmission over long distances, and then step-down the voltage for use in homes and businesses.

They are also used in electronic devices such as power adapters to convert the voltage of the a.c. power supply to a lower voltage suitable for the device.