Question

A metallic piece gets hot when surrounded by a coil carrying high frequency alternating current. Why?

Answer 1

Use the concept of eddy current for the induction of current in the metallic piece with coil having a high frequency alternating current. Also use the concept of induction heating because of which the metallic surface gets heated when surrounded by coil carrying high frequency alternating current.

Complete step by step answer:
When a metallic piece is surrounded by a coil carrying high frequency alternating current, the coil carrying current generates a changing magnetic field which in turn induces the current in circular paths in the metal surface. This current is called eddy current.
Due to this eddy current, the induction heating phenomenon occurs in the metallic surface.
This induction heating phenomenon causes the dissipation of the electrical energy into heat energy and hence, the metal being a good conductor of heat, gets heated.

Hence, the metallic piece gets hot when surrounded by a coil carrying high frequency alternating current.

Additional information:
The loops of currents that get induced in the conductor as a result of the changing magnetic field by the current induction process are called eddy currents.
The eddy currents are also known as the Foucault’s current.
The generation of heat in a material because of the eddy currents is known as the induction heating. The heat is generated as the material offers resistance to the eddy current.

Note:
One may get confused that eddy current is flowing through the coil itself then how the metallic surface gets heated. The students should be clear with the concept that the eddy current is induced in the conducting object placed near a coil carrying high frequency alternating current and not in the coil carrying current.