Why does every magnet have two poles, not just one? © Getty Images

Do magnets wear out?

Demagnetisation is a slow process but magnets can lose their strength over time. This generally happens in two ways.

Asked by: Barney Collins, by email

So-called permanent magnets are constructed from materials made up of magnetic domains, in which atoms have electrons whose spins are aligned with each other. This alignment is damaged over time, principally as the result of heat and stray electromagnetic fields, and this weakens the level of magnetism. The process is very slow, however: a modern samarium-cobalt magnet takes around 700 years to lose half its strength.

Read more:

Subscribe to BBC Focus magazine for fascinating new Q&As every month and follow @sciencefocusQA on Twitter for your daily dose of fun science facts.