Electromagnets
A coil with an iron core is called an electromagnet.
The iron core increases the coil鈥檚 magnetic field strength.
A simple electromagnet is made by coiling wire around an iron nail.
A simple electromagnet
Key points
Iron is easily magnetised and demagnetised.
Steel is more difficult to magnetise and is not easily demagnetised.
An iron core makes a temporary electromagnet.
It loses its magnetism as soon as the switch is opened and the current is switched off.
A steel core makes a more permanent magnet.
It does not lose its magnetism quickly when the current is switched off.
Electromagnets with iron cores are used:
- in scrap yards to lift magnetic materials such as iron and steel;
- to separate magnetic materials such as iron and steel from non-magnetic materials;
- in electric bells;
- in relay switches and door locks that can be controlled remotely;
- to hold open fire doors 鈥 the electromagnet switches off when a fire alarm is sounded and the doors close.