Alexander Fufaev
My name is Alexander FufaeV and here I will explain the following topic:

What Are Eddy Currents?

Explanation

Video

fufaev.org Eddy currents in a metal plate
Eddy currents in a metal plate - with and without slots.

Eddy currents - these are electrical, circular currents (induction currents) that form in extended, conductive materials, such as the base of an induction pot. If, for example, a metal plate is moved in an inhomogeneous magnetic field \(B\), vortex-like electrical currents are generated in the plate. These arise due to electromagnetic induction. This means that a changing magnetic field causes an electric field. This electric field in turn generates the eddy currents.

The movement of the metal plate is also damped. The reason for this is the Lenz rule (taken into account by the minus sign in the law of induction). According to Lenz's rule, nature generates eddy currents in such a way that they counteract their cause. The original cause of the eddy currents is the movement of the metal plate. Nature tries to slow down this movement. In this way, it prevents energy from being generated out of nothing.

In order to avoid eddy currents, slots can be cut into the metal plate to prevent the formation of electrical circular currents. This method is used, for example, with ferromanetic iron cores in the coils.