Horseshoe-shaped electromagnet used by James Joule, c.1840. This electromagnet was used by the scientist James Joule for experiments about energy. Joule was a Salford resident and the son of a brewer.

Permanent magnets can come in lots of different shapes and sizes. Bar magnets and horseshoe magnets are two of the most common shapes of magnet. The magnetic field is shown by lines with arrows ...