Physics · Explainer
How an induction cooktop heats the pan but not the counter
An induction cooktop never gets hot itself. A coil under the glass makes a fast-changing magnetic field, and that field drives swirling electric currents inside the iron pan sitting on top. The pan's own resistance turns those currents into heat, so the pan cooks while the glass and your hand stay cool.
The everyday puzzle
A normal stove works by getting hot and passing that heat to the pan. An induction cooktop breaks the rule: the cooking surface stays cool enough to touch moments after you lift the pan, yet the pan itself heated fast enough to boil water. Spilled sauce on the glass does not burn on.
It looks like magic, and it stumps a lot of people. The trick is that the heat is not coming from the cooktop at all. It is being generated inside the pan.
A changing magnet makes electricity flow
The key fact, discovered by Michael Faraday, is that a changing magnetic field pushes electric current through nearby metal. Not a steady magnet, a changing one. Move a magnet past a coil of wire and current flows in the wire; hold it still and nothing happens.
Under the glass of an induction cooktop is a coil carrying rapidly alternating current, which creates a rapidly changing magnetic field just above the surface. Set an iron pan in that field and the field drives looping currents, called eddy currents, round and round inside the metal of the pan itself.
Why the pan heats and the glass does not
Those eddy currents have to push through the pan's electrical resistance, and forcing current through resistance produces heat. So the pan becomes its own heater, warming from the inside out. The glass is not magnetic and carries no such currents, so it only warms later by contact with the hot pan.
This is also why induction needs the right cookware: a pan has to be magnetic, iron or magnetic stainless steel, for the field to grip it. The very same principle, a changing magnetic field driving current, is how power plants generate almost all the world's electricity and how a phone charges on a wireless pad. In the kitchen, it just means a cooktop that heats the food and not itself.
Sources & further reading
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