How does a microwave oven work?

A microwave oven is a radio transmitter in a metal box. Electrons whirl in a magnetron to make 12 cm waves that twist water molecules 2.45 billion times a second. A transformer, a capacitor and a diode turn mains electricity into about 4,000 volts.

Read how it works: How does a microwave oven work? · The history of the microwave oven · More boxes on Glassbox

Chapters in this interactive model

1. Inside a microwave oven: A metal box, a radio valve called a magnetron, and a lot of high voltage.
2. How a magnetron makes microwaves: Electrons whirl in a magnetic field past copper cavities that ring like whistles.
3. Why the food gets hot: Microwaves twist water molecules back and forth billions of times a second.
4. Standing waves and the turntable: Waves bouncing inside the box pile up into hot spots about 6 cm apart.
5. The door, the mesh and the switches: Holes much smaller than the wave act like solid metal.
6. What “50% power” really means: Most microwaves can’t turn down. They switch on and off instead.