Okay, does anyone know exactly what metal will do when i put it in the microwave (And put it on HI) and a scientific explaination as to why it happens?
thanks.
I’ve no doubt you’ll get better explanations than this, but for now:
Microwaves heat things by exciting their molecules. However they cannot pass through metal and get reflected (I think) instead. Since your microwave has a metallic interior, this is a Bad Thing and results in mini-lightning inside your microwave.
If you were to put a metallic object in your microwave and switch it on, you would see little lightning flashes inside. These can (IIRC) reach 2000[sup]o[/sup]C
There. Now where are the proper physicists?
pan
My experience has been that metal in a microwave heats up enough to incandesce and then light paper on fire. Someone left a twist-tie on his sandwich bag as he heated it up, and the paper part of the tie caught fire.
My son put a sandwich from Arby’s in our microwave to reheat it a couple of years ago. It was wrapped in their wrapper, which apparently had tin foil in it. What happened was not a pretty site. You never saw such a lightning storm as what went on in that microwave. :eek: Melted half the interior into a giant glob of goo. Ruined the sandwich to. Perfect waste of a 99 cent sandwich.
At any rate, the microwave is now resting comfortably in that great microwave junkyard in the sky. 
As for what causes the lightning, I think kabbes hit it pretty close.
I had always thought that the microwaves were “inducing” a current in the metal which then “grounded” itself somehow… I was way off there…
I don’t have a cite for this, (Google is probably YOUR friend), but I believe that on the newer microwaves (last 5 years or so), this doesn’t happen.
Which doesn’t help most of us, since we all bought microwaves when they were commercially hot, which was about 20 years ago. Mine STILL works!
From what I recall:
The microwaves create an electric field which rapidly changes directions back and forth (this is the property which cooks the food*). As far as I know any changing electric field will create a current on a conducting material.
A lower oven “power” setting would probably create a less spectacular effect, however, I don’t think you could prevent it.
*water (H20) is a dipole molecule, one half is positive (Hydrogen), and the other half is negative (Oxygen). Water molecules will align themselves with any static field; however, since the field created by the microwaves is constantly changing directions the water molecules essentially spin very rapidly. Long story short: this heats up the (whatever has water in it).
My son and I discovered that there’s a kind of toaster strudel that definitely doesn’t belong in a microwave. The paper looks like, well, just paper, but it seems that the inside is tinfoil.
The results are inedible, but they look real cool…sorta like you decorated the strudel with lots of little, shiny spiders.
It looked so neat we did it again.
From the Master: Why does metal produce strange effects in a microwave?
Microwave ovens bombard the interior of the oven with - wait for it - microwave radiation! They have a tube off to the side behind the control panel called a magnetron that creates microwave radiation and shoots it into the oven cavity. These microwaves then do much of what is mentioned above, such as making polarized molecules dance. Even the newer microwave ovens use the same microwave radiation, which will still fry thin or sharp metal. Note that some now come with metal racks, and even some of the older ones came with metal thermometers which you could insert into meat or other products while cooking. These racks and thermometers are nice and thick, though and have rounded edges, so the waves just bounce off them which out inducing any damaging current in them.
If you want a really good show try a can of WD-40, but do it outside away from anything flamable, and wear suitable protective gear.
Bizarre. I can only say that my version of events comes directly from the manual of my new microwave.
pan
Rysdad, this is for you!
Unwise Microwave Oven Experiments
Samples include: Cuppa burning plasma, Snifter of Neon, Foil-eating Plasma. Hours of fun for the whole family!
[sub]Do keep an eye on your son though…[/sub]
Some small metal things can go in the microwave though. Staples don’t seem to create any lightning.
Ok, I just have to share this because it’s so cool and this thread reminded me of it 
I used to buy microwave popcorn all the time, until I found a really good way to make it at home. Get brown paper bags and a bag of regular popcorn. Then put a tbls or two into a brown paper bag, fold the top down, put a staple in the top, and microwave it for about two minutes. Yummy popcorn for a few pennies, much better than the buck a bag microwave stuff.
Anyway, the staple doesn’t set the bag on fire or anything. I wonder why not?
Either: the staple is too small to create enough of a current to be hazardous. The foil and paper in the previous examples is a relatively huge area of metal compared to a staple.
or
The staple is covered by enough paper to prevent the interaction of microwaves with it. I’ve heard that small spoons can be left in food if they’re covered enough.
I have been thawing out frozen orange juice cans with top off but metal bottom still on and no sparks lightning or any other visual excitement. Was not sure why it worked but now thanks to SDMB I am armed with knowledge. ::dances around like Ed Grimley and puts in pocket protector::
Cool! I think I’ll try a couple of the candle things. (I’ve been thinking about getting a new microwave anyway…)
I think that if the metal object is touching the inner surface of the microwave, it in effect becomes part of the surface, so no sparks.
Also, to get sparks you probably need your metal object to be near the inner surface of the microwave with just air between the object and the surface.
pan
I have a original equipment metal rack that goes in the microwave oven.
One time, the food item that was on the bottom of the mic oven - under the metal rack which was across the middle - was touching the metal rack ever so slightly, and when I turned on the over one spot of the metal rack lit up and “arced” (if that’s the right word). Otherwise, I cook most meals with the metal rack in and no incidences.
I read a novel recently that featured a character who killed himself by rigging his microwave so that he could turn it on with his head inside. Not to be too grotesque, but does anyone know how long would it take and what exactly would happen?