Curious question about Microwave ovens

Old 12-29-04, 04:44 PM
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Curious question about Microwave ovens

This has nothing to do with safety related issues, but just wanted to know if there's any physics explanation behind an observation. Whenever I heat two coffee mugs in the oven, I seem to notice that they don't get heated up as quickly or even half as quickly as with heating individually the coffee mugs. Is there some kind of reflection happening or some interaction between the two mugs?
Old 12-29-04, 04:56 PM
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I'm certainly no expert on microwaves, but I've read that the more there is to heat the longer it takes, and that things heat faster on the outer edge of the microwave dish than in the middle.
Old 12-29-04, 05:05 PM
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I am not an electrician or a microwave expert either so this is from personal experience.
Microwaves as I understand it, bounce around inside of the unit and heat the food or beverage from the inside out. With the microwaves bouncing around 1 item, things heat quickly. Add another item and they now bounce around 2, each only catching about 1/2 of the waves each. This is why microwave sandwiches and tv dinners say to increase the cooking time for each additional item added.

To see if this works out, place 2 cups, one on top of the other(carefully) and see if they heat evenly. You have essentialy created 1 item out of the 2.

This is my understanding and others may have other and possibly better ideas or reasons.

Good luck with the morning coffee.
Old 12-29-04, 06:41 PM
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The magnetron tube transmits a certain amount of watts of energy. That energy is "bounced" around inside the oven. When a wave encounters food, the energy is absorbed by the molecules in the food item and cconverted to heat energy. The more food is in the oven, the more waves are absorbed and hence the smaller amount of wave energy which is absorbed by each item. Hence it takes a longer time to raise the temperature.
Old 12-29-04, 07:21 PM
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or even half as quickly
I think this is a perception problem. Two cups of coffee will certainly get at least as hot in two minutes as one cup will in one minute.

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