The magnetron is a vacuum-tube oscillator whose frequency is set by machined metal, not a tuned circuit, and almost everything people believe about why it cooks is wrong. Why 2.45GHz has nothing to do with water resonance, why food cooks from the outside in, the standing-wave cold spots the turntable exists to fix, why pointed metal arcs and flat metal does not, and inverter vs transformer power.
Electromagnetism
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How a Microwave Oven Actually Works -
How an Induction Cooktop Actually Works An induction cooktop has no hot element — the pan is the heating element, and the glass underneath stays cool until the pan warms it back. How a kilowatt of magnetic field becomes heat in the steel via eddy currents and hysteresis, why only ferrous cookware couples, the resonant inverter that drives the coil, the honest efficiency numbers against gas and radiant electric, and why it buzzes.