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how does the principle of electromagnetic induction apply to cooktops
The alternating current in a coil under the cooktop makes an alternating magnetic field. The changing magnetic field induces eddy currents in metallic cookware. With suitable cookware, the heating power from those ddy currents is bigger than the amount of heat directly generated in the coil, so the inductive system can be very efficient at transferring heat directly to the cooking pot. Gas flames throw out a lot of heat that just goes around the pot. Ordinary electric stoves heat up their own coil, with heat conduction carrying the heat over to the pot, but also usually out to other parts of the stove.
Some of the issues with inductive systems are discussed in a Wikipedia article. http://en.wikipedia.org/wiki/Induction_cooker
(published on 12/06/2007)
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