I just don’t get. Why can’t you?
You can.
I was hammered Monday night and threw a tinfoil plate of Chinese food into my nuker at about 3 AM. I cooked it for about 4 minutes and it was fine.
You can, but it’s not a good idea and not good for the oven to do this on a regular basis.
What happens is that the microwaves contact the metal and cause sparks that can start a fire or blow the uranium diode (or other component) that makes the microwave work in the first place.
I’ve done it. The sparking was cool. The smoking afterwards was not.
Robin
You can, but as long as there is a lot more food than metal, and that the metal has no sharp points - for the reasons described above…
[aside]
Put an incandescant light bulb (without its metal cap) in a microwave with the kitchen lights turned off for a new kind of light show…
[/aside]
Gp
Ms Robyn - I didn’t experience the sparking you describe when I performed this “experiment” on Monday night. The only other time I have placed metal in the microwave was during my junior year in high school. That was about 13 years ago. I did see sparks back then.
I humbly offer Cecil’s Classic Column Why does metal produce strange effects in a microwave?
Hmmm, should I start with a rant about how people can’t use the search anymore? Maybe link to about 10 previous threads? Nah, that’d be souch a spoilsport. Let’s answer the question!
First the basics:
Microwaves are oscilating electromagnetic fields. They heat food by accelerating weakly bound electrons. These electrons (being weakly bounded) cause whatever they’re bound too (your food) to move along. ergo, your frozen pizza is now hot.
Then some theory:
For most metals there is a so-called plasma frequency, for aluminium it is about 2E16Hz >> 2GHz of a normal mictowave oven… For frequencies under this the outer electrons behave as we read about them at school, i.e. a dispersed cloud, very weakly coupled to the atoms. (Especially true for the D-electrons!) This means that the electrons will have no problems whatsoever dancing along in the undulating E-field, and very little energy will be coupled to the atoms. Instead the undulating electrons will emit a new wave, and it is possible that all the energy will end up back in the magnetron. (Bad news for you. you’ll soon be shopping for kitchen appliances:)) It is also possible that there will be standing waves in the metal, and it might actually get hot enough to melt…
(I’d like to make some learned reference to how the value of epsilon changes with frequency, and how this can be put into Maxwells laws. Preferably saying that the E-field must be continous. But I’d have to look it up, and my books are still in boxes…)
From this we learn that metal per se is not dangerous, but that it interferes with the normal workings of the machine.
For more info than you’r ever possibly want, have a look at Unwise Microwave Oven Experiments.
(On preview I see that LNO found a better cite. (Although I’m dissapointed that there’s no mention to Maxwells laws.))
Put a CD in the microwave for about three seconds. You get a neat spark show, and then a pretty cool conversation piece.
I saw sparks in the lunchroom microwave this afternoon. And boy did the room smell. (Someone put a foil-wrapped something in there.)
Robin
FYI - steel wool makes for a very entertaining display as well.
I just saw a microwave that the whole inside is stainless steel. How do they do that without it sparking up at storm?
tc wrote:
I was with you until the last part. The microwave case is made of metal. I’m dubious that metal utensils placed in a microwave can harm the magnetron. I do this all the time. Can you find a cite explaining how that could happen?
Actually, I’m more concerned about foodstuffs. On rolls of Pillsbury Chocolate Chip Cookie Dough it says, rather ominously, “DO NOT MICROWAVE.” No explanation is offered. So . . . why not? I’m sure nothing worse than a big mess occurs (if that), but I’m still kinda curious.
(It’s a moot point, anyway; everyone knows that cookie dough is best prepared by leaving the roll in direct sunlight on a warm summer day for 30-45 minutes and then eating with a spoon).