325. What exactly goes on when you're cooking a potato in the microwave and it explodes?
A microwave oven heats food by depositing energy in its water. If you cook the food long enough, that water can begin to boil. If the food has a hard outer shell (e.g. a potato or a corn kernel), the boiling water can create enough pressure in the food to make it explode. That is what pops the corn in microwave popcorn and why the potato explodes if you don't pierce it so that steam can escape.