Eddy current is an induced current circulating in a metal disk or plate moving in a magnetic field.
When a metal plate is allowed to rotate or swing between the poles of a powerful magnet, the induced current flows through the plate in such a way that it tends to reduce or resist the motion of the metal plate producing it.
Eddy current acts as a breaking force because it slows down the movement and motion of a metal plate or disc in a magnetic field. This slowing down of the motion of a disc is called damping effect of eddy current
When a solid disc rotates in the magnetic field, the current is large and the disc is quickly brought to rest due to large opposing force provided by eddy current. If the disc is replaced with a disc containing slits, the slits increases the resistance of the disc and the eddy current is low allowing it to turn in the magnetic field for a longer time.
Uses of Eddy Current
- Damping of galvanometer – to control movement of pointers in moving coil meters
- Induction cookers or furnace to melting large amount of precious metals
- Used for detecting invisible crack in rail road which can endanger life
- eddy current generates heat in the cores of transformer, armature of electric motors and generators
- it also causes losses of energy and power
- it reduces efficiency of transformers, motors and generators