Electromagnets

When an electric current flows in a wire, it creates a magnetic field around the wire. This effect can be used to make an electromagnet. A simple electromagnet comprises a length of wire turned into a coil and connected to a battery or power supply.

A coil of insulated wire is wrapped around an iron nail. One end of the coil of wire is connected to a battery. The other is connected to a switch in the circuitA simple electromagnet

You can make an electromagnet stronger by doing these things:

  • wrapping the coil around a piece of iron (such as an iron nail)
  • adding more turns to the coil
  • increasing the current flowing through the coil

There is a limit to how much current can be passed safely through the wire because the resistance of the wire causes heating.

Dr Yan makes a powerful electromagnet by wrapping copper wire around pieces of iron and attaching a small battery

Electromagnets have some advantages over permanent magnets. For example:

  • they can be turned on and off
  • the strength of the magnetic field can be varied

These properties make electromagnets useful for picking up scrap iron and steel in scrapyards.

Electromagnet with scrap metal
An electromagnet being used in a scrapyard

The magnetic field of an electromagnet

The magnetic field around an electromagnet is just the same as the one around a bar magnet. It can, however, be reversed by reversing the current (turning the battery around).