How do microwaves work?

Question

Just curious how they heat up so quickly in so little time just using waves of energy.

Answer 1

The answer lies in the coupling coefficient of energy transfer. A standard gas or electric stove must heat itself, then the pot, then the food, all the while, it's radiating heat away.

In a microwave, the energy is directly coupled to the molecules and their bonds and does not directly couple with the cookware. The only reason the bowl gets hot is that the food's heat is being conducted into the bowl.

Answer 2

The reason microwaved food heats up so quickly is that conventional cooking heats the outside of the food and heat reaches the inside by conduction, which for most food is a slow process. Tryplacing a hamburger on a hot plate, place your hand on the top side of the hamburger and see how long it is before you feel the heat. Microwave ovens use radio waves with a frequency of 2450 MHz. These waves penetrate most foods to a depth of a few cm., so the inside starts heating up as quickly as the outside. The only complication is that microwaves don't heat all foods equally fast. Frozen foods don't absorb microwave energy as fast as thawed food. Dry foods like biscuits, uncooked rice and uncooked beans only heat up slowly. So if you heat a TV dinner in a microwave, you'll probably find that some items are hotter than others, and you'll need to let it stand for two or three minutes.

Answer 3

Microwaves take advantage of molecules that have a positive and a negative end (called a dipole), mostly water molecules. The microwave introduces a constantly shifting electromagnetic field into its chamber (where the food is) causing the molecules to literally spin back and forth trying to align with the magnetic field being introduced.

This motion of the molecules results in heat. And the production of heat is throughout the material, not just from the surface inwards.