What do electric bells, scrap-yard cranes and the central-locking in cars have in common? They all work using magnets, but not the permanent magnets of door catches and children's toys. The bells, cranes and car locks are based on electromagnets.
What is an electromagnet?
All electromagnets work on the principle that an electric current in a wire produces a magnetic field. In fact it is remarkably straightforward to make an electromagnet. Simply coil a length of wire round a piece of iron, such as a long iron nail, and pass an electric current through the wire. When the current flows a magnetic field is created and the iron becomes magnetised.