Posted by 5GJW [5thGenerationJW] on April 02, 1999 at 21:57:50 {ppHCdFLRUMlo6QIt25t6ZX9D1q7/.6}:
In Reply to: ***Common Sense Argument posted by Skeptic on April 02, 1999 at 18:46:22:
The chapter in my thermodynamics textbook that introduces the second law covers 24 pages, so it is not surprising that everyone is having a difficult time to reduce the law to a few sentences. I'll take a stab at what Jan was trying to say, and he can correct me if I misquote him.
When the books are arranged in a different order, their energy state does not change, assuming that they are put back on the same shelf. (If they were put on a higher shelf, they would have more potential energy, which you would notice if they fell off of the shelf.) It took energy to rearrange the books, but that energy was dissipated in the form of heat, and not transferred to the books. The heat flowed from a warmer body to a colder body, as the second law requires. Now, here is the tricky part. If you put the books back in their original order, you would not get this heat back, it is not a reversible process. The heat will not flow from a colder body to a warmer body, that would be in violation of the second law. This is why the first law, that energy is conserved, is not enough to explain what is happening here. The second law relates to systems finding an energy equilibrium, which has been referred to here as a disordered state. The ordered state is a state where one system is at a higher energy level than another.
5GJW, who will hold you responsible for knowing this on the midterm