te:
cup and >the liquid in it will heat up, it really doesn't matter which one = heats the >other.
hough they may spark (or not, depends a bit on the shape and size). =A0We u= se aluminum foil to keep the corners of brownies from burning - the metal b= locks the wavers.
that >are agitated by the uwaves and get hot. Take two equal teaspoon full= s of water >and rubbing alcohol, put into two equal-sized pyrex dishes, and= turn on the >uwave. Both will get hot and eventually boil off.
To be pedantic, a metal cup holding liquid will heat up.
I'm still wondering if, lacking a spark, gasoline vapors would ignite.
Harry K