|MLA Citation:||Bloomfield, Louis A. "Question 571"|
How Everything Works 18 Jun 2018. 18 Jun 2018 <http://howeverythingworks.org/print1.php?QNum=571>.
However, there is no analogous way to reach inside the food and extract its thermal energy. You must wait for the thermal energy inside the food to drift to its surface and to be transferred to the colder surroundings. This requirement is the result of the laws of thermodynamics, which govern the interconversions of work and heat. While it's easy to turn mechanical work into heat (just rub your hands together), it's very difficult to turn heat into work. Because of this difficulty, thermal energy must usually be transferred elsewhere. You can't build a "microwave refrigerator" that turns thermal energy into microwaves inside the food.