Eddy currents are the currents induced in the body of a conductor when the amount of magnetic flux linked with the conductor changes.
For example when we move a metal plate out of a magnetic field,the relative motion of the field and the conductor again induces a current in the conductor.The conduction electrons making up the induced current whirl about within the plate as if they were caught in an eddy(or whirlpool) of water. This is known as eddy current.
Its magnitude is given by: i=(induced emf/resistance)