What are eddy currents?

Eddy currents may be defined as currents induced in a thick conductor when it is placed in a changing electric field. Consider a metallic block placed in a continuously changing magnetic field by keeping the block fixed and changing the magnetic field with the help of an alternating current. Due to the continuous change of magnetic flux linked with the block, induced currents will be set up in the body of the metal block. These currents assume a circular path and the direction is such that it opposes the change producing it (according to Lenz’s Law). These currents look like whirlpools in a fluid, and hence called eddy currents.