How Induction Works
At its simplest, an electrical current in the cooktop is used to produce a magnetic field. Placing the pan on the cooktop in the magnetic field induces a circulating electrical current in the base of the pan. The resistance to the current causes the pan to heat up.
But how does it really work?
OK, lets back up a little. How does a gas or regular electric cooktop work? Either there is a gas flame or a an electric heating element below the pan. Either of these gets hot and heats up the pan. If it is gas it heats up that metal grid supporting the pan as well, or if it is electric it tends to heat up the surrounding surface area. Because the pan gets hot, the contents of the pan in turn get heated up and hey presto, cold coagulated baked beans from a can become piping hot in beautiful tomatoe sauce and all ready to go on a slice of toast. Maybe with a shake of pepper and a dash of worcestershire sauce. (You get the idea, if you prefer, substitue chicken noodle soup for the baked beans on toast.) Meanwhile a fair amount of heat has escaped around the pan to the kitchen in general.
In the case of an induction cooktop, the surface does not get hot. The only thing that is directly heated is the base of the pan itself (and once the pan is hot, so the food can start to cook.) Yes, there will be some warming back to the cooktop from the pan but this is a side effect. The induction cooktop does not work by heating the cooktop itself! One instant benefit is that you kitchen should not heat up so much. There will not be all that heat escaping around the sides of the pan. Why does the pan get hot? OK, my attempt in laymans terms that I understand. Think of a good old fashioned electric cooktop with one of those circular coils that go from dull grey to bright orange (hot) when turned on. Or think of an electric heater - again there is some sort of element that gets hot. This happens because electricity is passed through it and there is resistance to the free flow of the electricity. This resistance causes the element to heat up. Even a regular light buld works like this - a thin wire resists the electricity flowing through it, heats up to white hot and gives off light and heat. The base of the saucepan is our resistor for an induction cooktop. The electro magnet in the induction cooktop INDUCES a circulating electrical current in the base of the pan. (If you really want to know more, google "eddy current" and"hysteresis"). This criculating current cannot move as freely as it would like due to the resistance in the metal that makes up the base of the pan and so this metal gets hot.