Microwave Ovens

[c00ky83]

Last night I heated a plate in my microwave.  Don't ask why, I just needed a warm plate.  Two minutes later the microwave was on fire - the rotating bit above the plate was alight.  Now I know this wasn't the best idea, probably one of my worst in fact...but how does the physics behind this work?  My guess is the waves simply bounced off the plate and heated the bit above the plate.  Any ideas?

[magicdice]

microwave ovens produces waves with a frequency that is only marginally different from the resonant frequency of water - this means that the water molecules vibrate like crazy, so gets hotter, which is conducted through all the other molecules and so the food gets hot.

 

plates don't contain an awful lot of water

[Gandy]

you should of put a glass of water in there as well.  Plates normally only take 1 minute in the microwave.  Don't forget to let them stand though or they won't be cooked properly and you'll get ill.

[Headtime]

I regularily heat plates in the microwave. Even though I understand that microwaves work by vibrating water molecules, they do heat up plates.

I also have a small plastic bowl, that gets preposterously hot when heated in the microwave even for a short time.  I've never understood why when plastic contains no water.

[Headtime]

The above post was meant to say, that I don't think heating the plates would have damaged your oven. It was probably another fault.

The glass of water idea is probably not bad.

[c00ky83]

Thanks, some helpful answers - particularly Headtime. The oven is quite old, like a widescreen TV compared to the latest models, so I did think maybe it wasn't my fault. I sure won't try it again though.

[Gandy]

It was in my student days where we thought of the glass of water idea.  To soften hasish you heat it up.  We tried the microwave but it just dried it out.  Someone thought of putting a glass of water in there too and it worked fine.  I am trying to work out whether the time saved by doing this out weighed the time wasted my smoking hash.  Oh well, we're only young once!!

[landie]

Sorry I'm a bit late with this answer, been having trouble posting answers on the new format site.

If you use your microwave with no food in it you run the risk of permanently damaging the Magnatron (device which creates the microwaves). The microwave is really designed for heating-up foodstuffs and you should not use for the heating of tableware alone. As others have said, I always leave a bowl of water in mine in case I switch it on accidentally. An empty microwave is a dangerous place when switched-on.

Hope this belated answer helps.

[newtron]

While heating up food in a microwave, I've noticed that some plates get really hot fast while others don't heat up as quickly.  So some property of the plate affects the way it reacts in the microwave. I know some glazes used on ceramics contain metals and I know that you are not supposed to put metal in the microwave.  Could this be the cause?

[BillyBB]

Normally the microwave energy is absorbed by the food and turned to heat. With nothing to absorb the microwaves it has overheated something else.

Some plates are microwave safe and others aren't. If it gets REALLY hot it's not.