Circulating currents called eddy currents are induced in large or bulk pieces of metal in a changing magnetic field. Hence, an eddy current is the current which is induced in little swirls on a large metal.
When a metal plate swings into a magnetic field, the change in flux will induce an e.m.f., cause the free electrons to move and creates swirling eddy currents.
- According to Lenz’s law, the magnetic poles produced by the current should repel the poles of the magnet as the plate enters the magnetic field. Similarly, the poles produced by the current should attract the poles of the magnet as the plate leaves the magnetic field.
- These two actions will give rise to a force that damps the oscillation of the plate and slows it down till it comes to a stop
Disadvantages of eddy currents:
- Heats up the metal and transform useful forms of energy into heat.
- Formation of a retarding force to motion.
- Reduce the efficiency of devices that makes use of electromagnetic induction.