What is an eddy current? Discuss the practical applications of eddy currents. What should be done to decrease the effects of eddy currents?

(N/A) We have studied electric currents induced in well-defined paths in conductors like circular loops. Even when bulk pieces of conductors are subjected to changing magnetic flux,induced currents are produced in them. However,their flow patterns resemble swirling eddies in water. This effect was discovered by physicist Foucault ($1819$-$1868$) and these currents are called eddy currents.
Consider the apparatus shown in the figure. $A$ copper plate is allowed to swing like a simple pendulum between the pole pieces of a strong magnet. It is found that the motion is damped and in a little while,the plate comes to a halt in the magnetic field.
We can explain this phenomenon on the basis of electromagnetic induction. The magnetic flux associated with the plate keeps on changing as the plate moves in and out of the region between magnetic poles. The flux change induces eddy currents in the plate.
The directions of eddy currents are opposite when the plate swings into the region between the poles and when it swings out of the region. Eddy currents are often undesirable since they heat up the core and dissipate electrical energy in the form of heat. To reduce these effects,the core is often laminated or slotted to break the paths of the eddy currents.
Eddy currents are used to advantage in certain applications like:
$(1)$ Magnetic braking in trains: Strong electromagnets are situated above the rails in some electrically powered trains. When the electromagnets are activated,the eddy currents induced in the rails oppose the motion of the train. As there are no mechanical linkages,the braking effect is smooth.
$(2)$ Electromagnetic damping: Certain galvanometers have a fixed core made of non-magnetic metallic material. When the coil oscillates,the eddy currents generated in the core oppose the motion and bring the coil to rest quickly.
$(3)$ Induction furnace: Induction furnaces can be used to produce high temperatures and can be utilized to prepare alloys by melting the constituent metals. $A$ high-frequency alternating current is passed through a coil which surrounds the metals to be melted. The eddy currents generated in the metals produce high temperatures sufficient to melt them.
$(4)$ Electric power meters: The shiny metal disc in the electric power meter (analogue type) rotates due to the eddy currents. Electric currents are induced in the disc by magnetic fields produced by sinusoidally varying currents in a coil.