A perpetual-motion machine of the second kind

The important thing about Eq. (8.4) is that W y is the sum of two terms, each associated with a different temperature. We might imagine a complicated cyclic process involving many heat reservoirs at different temperatures for such a case 

It is possible to devise a cyclic process so that J%y is positive that is, such that after the cycle, masses are truly higher in the surroundings. It can be done in complicated ways using reservoirs at many different temperatures, or it can be done using only two reservoirs at different temperatures, as in the Carnot cycle. However, experience has shown that it is not possible to build such an engine using only one heat reservoir (compare with Section 7.6). Thus, if 

This experience is embodied in the second law of thermodynamics. It is impossible for a system operating in a cycle and connected to a single heat reservoir to produce a positive amount of work in the surroundings. This statement is equivalent to that proposed by Kelvin in about 1850. 

The Carnot engine with its two heat reservoirs is usually represented schematically by a drawing such as that in Fig. 8.1. The work W produced in the surroundings by the reversible engine Er is indicated by the arrow directed away from the system. The quantities 

---

If such a machine could be constmcted, it would be a perpetual-motion machine of the second kind. ... 

The transformation of heat into work is not the only process which takes place in the steam engine, as it would be in a perpetual motion machine of the second kind. A certain quantity of heat has also been removed from the boiler at a high temperature and given up at a lower temperature to the condenser. In practice we find, therefore, that a machine working periodically can convert heat into work if at the same time it takes a certain quantity of heat from a source at a high temperature and gives it up again to a sink at a lower temperature. 

A statement perfectly comprehensible in macroscopic, operational terms. A cyclic engine that converts all heat to work is shown in Fig. 3.5. Since the reservoir or the exterior only loses heat, inequality (3.3.8) is clearly violated. This engine is sometimes called a perpetual motion machine of the second kind and the Second Law is the statement that such a machine is impossible. The... 

If heat could pass spontaneously from a colder body to a hotter body, then a perpetual motion machine of the second kind could be realized by simply making the heat Q2 expelled by a cyclic heat engine to the colder reservoir pass by itself to the hotter reservoir. The result would be the complete conversion of the heat (<2i — Qi) to work. 

No violation of either physical statement of the second law of thermodynamics has ever been observed in a properly done experiment. We regard the second law as a summary and generalization of experimental fact. A machine that would violate the Kelvin statement of the second law and turn heat completely into work in a cyclic process is called a perpetual motion machine of the second kind. 

Elixirs of youth are perpetual motion machines of the second kind. They violate the second law of thermodynamics. Life is highly organized and requires energy to maintain this order, a machine (the fountain of youth) that can magically create order out of the normal process of the forward arrow of time must violate the second law. 

Q. 10.3 An inventor sends a patent application to the Patent office. In it (s)he claims to have found a chemical compound ensures eternal youth for all who drink it. The patent office rejects it on the basis that the formulation is a perpetual motion machine. Explain why. Did they reject it because it was a perpetual motion machine of the first or second kind ... 

---