Pocket Genius Science: Energy and forces – Electromagnetism

Facts At Your Fingertips: Energy and forces – Electromagnetism

An electrical current always produces a magnetic field around it.

Electromagnets are made by passing electricity through a wire that has been wrapped around a piece of iron. Unlike permanent magnets, an electromagnet loses its magnetism as soon as the electrical current is switched off.

How an electromagnet works

To make an electromagnet, a copper wire is wrapped tightly around an iron core.

When electricity passes through the wire, the iron core is turned into a magnet.

The stronger the electrical current, and the more times the wire is wrapped around the core, the stronger the magnet will be.

Making sounds

Speakers use electromagnets to make sounds.

Electricity flows through a small electromagnet inside the speaker. Changes to its magnetic field causes a cone to vibrate.

We hear these vibrations as sounds. Varying the strength of the electrical current changes the volume of the sound produced by the speaker.

Lifting metals

Scrapyards use powerful electromagnets to pick up and move heavy objects. Only magnetic materials such as iron are attracted to the magnet.

Electromagnets are also used to separate magnetic metal from non-magnetic materials so that it can be recycled.