The Physics Question Bank

A transformer changes the size of an alternating voltage. It only works with alternating current because the magnetic field needs to keep changing.

A transformer has two coils of wire wrapped around an iron core. The input coil is called the primary coil and the output coil is called the secondary coil.

When an alternating current flows in the primary coil, it produces a changing magnetic field in the iron core. This changing magnetic field passes through the secondary coil. The changing magnetic field then induces an alternating voltage across the secondary coil.

If the secondary coil has more turns than the primary coil, the transformer is a step-up transformer. The output voltage is higher than the input voltage.

If the secondary coil has fewer turns than the primary coil, the transformer is a step-down transformer. The output voltage is lower than the input voltage.

In an ideal transformer, the power input is equal to the power output. This means that if the voltage increases, the current decreases. If the voltage decreases, the current increases.

6-mark answer split into marks

1 mark: A transformer changes the size of an alternating voltage.

2 mark: It has a primary coil and a secondary coil wrapped around an iron core.

3 mark: An alternating current in the primary coil produces a changing magnetic field in the iron core.

4 mark: The changing magnetic field passes through the secondary coil and induces an alternating voltage.

5 mark: If the secondary coil has more turns than the primary coil, the transformer steps up the voltage.

6 mark: If the secondary coil has fewer turns than the primary coil, the transformer steps down the voltage.