Perpetual motion machine of the second

There are many equivalent statements of the second law, some of which involve statements about heat engines and perpetual motion machines of the second kind that appear superficially quite different from equation (A2.T21). They will not be dealt with here, but two variant fonns of equation (A2.T21) may be noted in... 

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. 

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. 

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. 

The second law of thermodynamics An isolated system, if not already in its state of thermodynamic equilibrium, spontaneously evolves toward it. Thermodynamic equilibrium has the greatest entropy among the states accessible to the system. Perpetual motion machines of the second kind are thus impossible. 

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. 

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