Why can't you run a microwave empty?

Question

Obviously there is no reason to run one empty, but I've always been told that its a really bad thing to do... why?

Answer 1

Because the electromagnetic fields inside it will build up to extremely high levels. Since the walls of the oven are mirrorlike and the plate is almost perfectly transparent to microwaves, the electromagnetic waves streaming out of the oven's magnetron tube bounce around endlessly inside the oven's cooking chamber. The resulting intense fields can produce various types of electric breakdown along the walls of the cooking chamber and thereby damage the surface with burns or arcs.

Furthermore, the intense microwaves in the cooking chamber will reflect back into the magnetron and can upset its internal oscillations so that it doesn't function properly. Although magnetrons are astonishingly robust and long-lived, they don't appreciate having to reabsorb their own emitted microwaves.

Answer 2

Running Microwave Empty

Answer 3

Microwaves work by emitting long wavelength electromagnetic waves (longer wavelength than visible light). The microwaves release many of these waves. When these electormagnetic waves hit the food they are absorbed by teh ater molecules in the food, which increases the temperature in the food. When there is nothing in a microwave all of the energy in the electromagnetic waves are absorbed by the microwaves electrical apparatus. If the temperature of the electrical parts of the microwave gets too high then the microwave will break.

Answer 4

There is no reason why running a microwave empty would be bad, other than the waste of energy. Even when you cook something in it, the food only takes up some of the space inside. Since the microwaves fill the inside of the oven entirely, and are nor directed onto what is being cooked, it does not make sense to say the microwaves will damage the oven itself if there is nothing inside the oven.

Answer 5

Because, with no food to soak up the energy, the oven itself gets it all. Many years ago a microwave I had somehow got left on empty for several minutes and the glass plate shattered from thermal stress.

Answer 6

It depends on the microwave.

Running it empty cause the microwaves to reflect around (there is nothing to absorb them) and some will then reflect back into the magnetron. Some magnetrons do not cope at all well with this.

Mine is just fine run empty, or even with metal plates etc in it.

Answer 7

I would assume it is because there is nothing to soak up the radiation that is emitted and therefore it will either A) Leak out (potentially dangerous in high enough doses) or B) will accumulate within the microwave perhaps leading to an explosion...?

Try it. And stand well back...

Answer 8

The microwaves would be reflected round

Answer 9

microwave oven works by charged particle.
but in empty space it stays in and can cause damaged to your skin; even to your dna.
so do not try it even

Answer 10

as the microwaves will damage the cavity