Modern Physics for Engineers Lecture slides 18b – Entropy and heat flow

This lecture part describes how the flow of heat from hotter to colder bodies leads to an increase in entropy overall, with the entropy of the hotter body decreasing but the entropy of the cooler body increasing by more. A numerical example is given to show just how enormously unlikely it is that even a small amount of heat would instead flow from cold to hot. In turn, this justifies the second law of thermodynamics. (slides)