What is a transformer?

The voltage of an alternating current can be changed using a device called a

transformer

.

A transformer contains two coils that are wound around a soft

iron core

.

iron core

The alternating current in the

primary

(

input

)

coil

produces an alternating magnetic field.

This alternating magnetic field induces an alternating current in the

secondary

(

output) coil

.

primary coil secondary coil

How does a transformer change voltage

?

The

voltage induced

in the secondary (output) coil depends on the

number of turns

on the primary and secondary coils. A

step-up transformer

has more turns on the secondary coil and so

increases voltage

.

A

step-down transformer

has fewer turns on the secondary coil and so

decreases voltage

.

Where are transformers used?

A television needs a very high voltage to operate. It contains a

step-up transformer

, which increases the voltage of the electricity supplied to the television.

This outdoor transformer decreases the voltage of the electricity carried by the national grid. It is an example of a

step-down transformer

.

How are transformers used to supply electricity?

How does electricity get to your home?