Eddy currents are usually undesirable and equipment is designed to minimize them, but sometimes they can be put to good use. In the induction furnace, which consists of a a crucible surrounded by a coil of copper tubing, eddy currents are used to melt metal.
The copper tubing coil carries high frequency alternating current. When metal is put into the crucible, the rapidly changing magnetic field produced by the alternating current produces eddy currents in the metal, heating it so that it melts. The coil itself is kept cool by water pumped through it – this is the reason why the coil is made of copper tubing.
The induction furnace is widly used in metal recycling. Metal must be melted before it can be reused.