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Uses of Magnets

There are four main types of uses of a permanent magnet:

1. To attract or repel, e.g. there is a magnet in the rubber lining of a fridge door that holds it shut.

   

2. to convert mechanical energy to electrical energy, e.g. in a generator of electricity.

   

   There has to be an external force (not shown) that rotates the coil in between the magnets. This could be a water turbine, or a bicycle wheel. When the coil moves, the magnetic field induces a voltage.

3. to convert electrical energy to mechanical energy, e.g. in a motor.

   

   A battery provides the current. When a current flows in the coil, the magnetic field produces a force that rotates the coil.

4. to guide electron beams, e.g. in cyclotrons.

   

   A charged particle moving in a magnetic field is forced to go round in circles. In a cyclotron, a special device (not shown) speeds up the particle. Cyclotrons are used to accelerate protons to treat cancer, for nuclear physics experiments, and to produce medical isotopes.

Electromagnets are used in many electrical devices, such as relays, circuit-breakers and loudspeakers. Other examples are in scrap yard to remove iron, the older type of televison, and transformers.