Science Notees

(1) how an induction cook top on an electric range operates by making use of eddy currents.

An induction cooker transfers electrical energy by induction from a coil of wire into a pot made of material which must be electrically conductive and ferromagnetic. The heat generated is analogous to the unwanted heat dissipated in an electric transformer; most of the heat is due to resistive heating like a transformer's copper losses and eddy currents and the rest is analogous to a transformer's other iron losses.

A coil of wire is mounted under the cooking surface, and a large alternating current is passed through it. The current creates a changing magnetic field. When an electrically conductive pot is brought close to the cooking surface, the magnetic field induces an electrical current, called an "eddy current", in the pot. The eddy current, flowing through the electrical resistance, causes electrical power to be dissipated as heat; the pot gets hot and heats its contents by heat conduction.

Induction cooking, 14 febarary2012, design of Induction cooking {online}

http://en.wikipedia.org/wiki/Induction_cooking (accessed 28 February2012)

How Induction Cooking Works:

The element's electronics power a coil (the red lines) that produces a high-frequency electromagnetic field (represented by the orange lines).

That field penetrates the metal of the ferrous (magnetic-material) cooking vessel and sets up a circulating electric current, which generates heat. (But see the note below.)

The heat generated in the cooking vessel is transferred to the vessel's contents.

Nothing outside the vessel is affected by the field--as soon as the vessel is removed from the element, or the element turned off, heat