Grades 6–8 · Everyday Life
How can a cooktop heat a pan without a glowing burner?
An induction cooktop puts a coil beneath its glass surface. Electronics send alternating current through the coil. The current repeatedly changes direction, so the magnetic field around the coil changes too.
In the diagramThe pan becomes the heaterA changing magnetic field induces currents in the metalGlass surfaceCoil with alternating currentInduced currents meet resistanceSupplied example: I²R = 12 W in a resistive loop.
That changing field induces electric currents in a suitable metal pan. The pan resists those currents, converting electrical energy into thermal energy. In this way the pan itself becomes the heater. The picture separates the coil, the field and the induced current so the hidden connection is easier to see.
A simple resistive-loop example illustrates this conversion. If the effective current is 2 amperes and the resistance is 3 ohms, the heating power is current squared times resistance: 2 × 2 × 3 = 12 watts. These are supplied values for an imaginary loop, not a calculation of a real cooktop or its pan temperature.
Ordinary induction cooktops need suitable cookware, commonly with a magnetic steel or iron base. The glass can still become hot through contact with a hot pan. There is no need for a red-hot coil above the glass, but energy still has to come from the electrical supply.
About this explanation
Starting knowledge: Understand electric current, resistance and energy transfer.
Sources
- Bosch — How do induction cooktops work?
- U.S. Department of Energy — Making the Switch to Induction Stoves or Cooktops