How does a microwave heat food without any flame or hot coil?

Hook

Why and how does a microwave heat food without any flame or hot coil? You press a button, and two minutes later your leftovers are steaming. The secret is an invisible wave that makes water molecules wiggle.

Wave

Microwaves are a type of electromagnetic wave, like radio waves and light. Most home microwave ovens use waves at about two point four five gigahertz, meaning the field flips direction billions of times every second.

Magnetron

Inside the oven, a part called a magnetron makes those waves. They bounce around the metal box and pass into the food.

Water

Water molecules are polar. One end is slightly positive, and the other slightly negative. As the field flips back and forth, the molecules keep twisting to line up with it.

Heat

All that jostling turns the wave's energy into heat. Fats and sugars can heat too, but water is the main reason food warms up.

Inside

A common myth says microwaves cook food from the inside out. They don't. The waves only reach about an inch or so in, and the heat spreads inward from there. That's why thick food can stay cold in the middle.

Spots

Waves also bounce and overlap, making hot and cold spots. That's why many microwaves have a turntable, and why stirring halfway through helps.

Close

So a microwave uses fast flipping waves to twist water molecules, and that motion becomes heat. ThatsWhyHow.