Lecture 15: Refrigerators and Path Dependence of Work

How refrigerators work. Why you can't cool your apartment by leaving the refrigerator door open. How heat and work depend on which path is taken. How to do completely meaningless work, the kind that's turned entirely into heat. We prove why the free energy is a useful concept: it tells you the maximum amount of work you can expect to extract from a system. The free energy is about the useful energy. We show that chemical potentials drive chemical work. How to levitate Tosanumi the sumo wrestler with superconductors and magnets, and how much work the superconductor does in the process.
Class discussions: The heat death of the universe. (Don't worry -- the sun will die out far before that.) More about high temperature superconductors, and possible applications.

Lecture Audio