[Phys-L] Re: metal in microwave oven?

[Chuck Britton <britton@NCSSM.EDU>]

Shallow aluminum 'TV dinner' type containers have been sold with
microwave instructions for some time.

Leaving a spoon in your coffee cup won't be very exciting (unless the
handle comes close enough to the (metal) wall to arc).

Microwave ovens heat by way of induced currents and joule (resistive) heating.
(There is no resonance involved - as I learned from a friendly
microwave spectroscopist.)

If the metal is a good conductor - there will be little resistive
heating and lots of reflection.
Likewise - a good insulator won't have the induced currents.

Check the bottom of your next popcorn bag and note the dark insert.
This material is 'tuned' to be an excellent absorber.
Not too conductive (reflective) - not too insulating (transparent).

(But yes - with a little effort, you CAN generate ball lightning in
your home oven. A Google search on ball lightning should work. Look
at eskimo.com for this and other weird science stuff)


At 12:26 PM -0500 3/22/05, Anthony Lapinski wrote:
> On a recent ski trip to Colorado, my friend brought a can of soup on the
> mountain. He opened the top, and heated the soup can in the microwave! I
> found this hard to believe. I thought that any metal placed in a microwave
> oven will produce sparks and damage the interior. Apparently, I was
> mistaken. Can someone clarify the physics of metals in microwaves for me?
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