6.0 Eddy Current:

In the last section we have studied the induced electric current in a circular loop. Their path of current was well defined. If a sheet of metal is moved in a strong magnetic field (shown in figure). Current induced in little swirls in a metal sheet.

Consider a sheet of metal is moving in a magnetic field. Assume an arbitrary loop b in metal sheet shown in figure. As it is moving in, area is changing and so magnetic flux is changing. We know as magnetic flux through a conducting loop(b) change, current is induced in loop. There may be many number of loops on the sheet hence current is induced on the surface in many paths. These current is called eddy currents.

If a sheet of metal is swung into a strong magnetic field. It will stop as it starts to move through the field. All of it kinetic energy will cause a major change in magnetic field. Because of eddy currents in sheet thermal energy is produced into it. This energy comes out in form of heat. This is known as electromagnetic dumping. To get rid of these currents slits are made in metals so eddy currents cannot occurs in large amount. Eddy current is undesirable because they heat up the metallic core and dissipate electrical energy in form of heat. So this phenomena of making slits is used to reduce eddy currents in metallic core of transformer, electrical motors etc.