Question

Eddy currents are produced in a metallic conductor when
(A) The magnetic flux linked with it changes
(B) It is placed in a changing magnetic field.
(C) It is placed in a magnetic field
(D) Both A and B

Answer 1

Hint:To solve this question,we have to understand about the concept of induced emf generated by change in magnetic flux and as a result of this eddy current is produced in the shape of a whirlpool.

Complete step by step answer:
Eddy Currents are the currents induced in the body of a conductor when the amount of magnetic flux linked with the conductor changes. These were discovered by Foucault in the year$1895$ and hence they are also called Foucault currents.
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 the induced current whirl about within the plate as if they were caught in an eddy (or whirlpool) of water. This is called the eddy current.
$i = \dfrac{{induced\,e.m.f}}{{resis\tan ce}} = \dfrac{e}{R}$
But $e = \dfrac{{d\phi }}{{dt}}$
$\therefore \,\,\,\,\,\,i\,\, = \, - \dfrac{{\dfrac{{d\phi }}{{dt}}}}{R}$
So, from the above discussion it is clear that eddy current corresponds to change in magnetic flux. So, eddy currents are produced when magnetic flux linked with it changes.
Hence, option (A) is the correct option.

Note: That eddy currents are basically the currents induced in the body of a conductor due to change in magnetic flux linked with the conductor. This change in flux can be done by either changing area or non-uniform magnetic field.