Question

Eddy currents are produced in a material when it is
A) Heated
B) Placed in a time varying magnetic field
C) Placed in a electric field
D) Placed in a uniform magnetic field.

Answer 1

Hint: Eddy currents are currents which circulate in conductors like swirling eddies in a stream. These loops of electric current are induced within conductors by a changing magnetic field in the conductor.

Complete step by step answer:
We are given to find when the eddy currents are produced in a material.

Eddy currents are the loops of electric current which is induced in a conductor by a change in the magnetic field. According to Faraday’s law of induction, the change in magnetic field induces an electric current in the conductor.Eddy currents flow in closed loops within the conductors and they flow in planes which are perpendicular to the applied magnetic field.For eddy current to occur, there has to be a non-uniform magnetic field. So if the magnetic field varies with time, then the field will be non uniform. Hence, the correct choice is Option B, eddy currents are produced when a material is placed in a uniform magnetic field.

Additional Information: The heating effect of eddy currents is used in melting the metal in an induction furnace. Rapidly changing magnetic fields can cause dangerous eddy currents in our body as they produce large amounts of heat.

Note: Eddy current can be created by an AC electromagnet or transformer. Eddy currents and induce currents are different. Induced currents are the currents induced by a change in magnetic field whereas eddy currents occur when the induced currents then generate magnetic moments in the same conductor. Do not confuse eddy currents with induced currents.