What are Eddy currents? State its two applications.

Answer: Eddy currents are the circulating induced currents set up in the body of a conductor when the magnetic flux through it changes. Applications: electromagnetic (eddy-current) braking and induction furnace (also dead-beat galvanometer, speedometers).

Eddy currents: When a bulk piece of metal moves in a magnetic field, or is placed in a changing magnetic field, closed loops of induced current flow inside the metal like whirlpools (eddies). By Lenz’s law they oppose the change that produces them. They were first observed by Foucault, so they are also called Foucault currents.

Applications (any two):

1. Electromagnetic brakes: in electric trains, a strong field applied to a metal drum on the wheels sets up eddy currents that oppose the rotation and slow the train smoothly.
2. Induction furnace: a high-frequency alternating current in a coil produces large eddy currents in the metal placed inside it, heating it enough to melt it.
3. Dead-beat galvanometer: eddy currents in the metal frame of the coil bring the coil to rest quickly.
4. Speedometers and energy meters.