Question

what are advantages and diadvantages of eddy current?

Answer 1

Eddy Current :
   Eddy currents are loops of electrical currents induced within conductors by a changing magnetic field in a conductor due to Faraday's law of induction.
Advantages of eddy Currents:
   (i). Electromagnetic damping: When a mettalic frame or plate oscillates in a magnetic field (e.g. in a dead-beat galvanometer), the eddy currents generated in the frame or plate oppose the motion of the frame and bring it to rest as the oscillations die out quickly. This is called electromagnetic damping.
   (ii) Magnetic Braking: This is provided in electric trains by placing strong electromagnets above the rails. During breaking, the metal wheels are exposed to a magnetic field generated by electromagnets, generating eddy currents in the wheels. The magnetic interaction between the applied field and the eddy currents acts to slow the wheels down. The faster the wheels are spinning, the stronger the effect, meaning that as the train slows the braking force is reduced, producing a smooth stopping action.
   (iii). Induction furnace: In an induction furnace, high frequency alternating currents are passed through a coil surrounding the metals to be melted. The eddy currents generated in the metals produce high temperatures sufficient to melt it.

Disadvantages of eddy currents:
   i). Heats up the metals and transform useful form of enegy into heat.
   ii). Formation of a retarding force to motion.
iii). Reduce the efficiency of devices that makes use of electromagnetic induction.