Perpetual motion of the second kind

Principle of Thomson (Kelvin) It is impossible to devise an engine that, working in a cycle, would produce no effect other than the extraction of heat from a reservoir and the performance of an equal amount of work ( perpetual motion of the second kind ). 

If this were not so and work had been done on or by the system by interchange of heat with the surroundings, we could use the cycle to obtain perpetual motion of the second kind. 

A consequence of the impossibility of converting heat isothermally into work in a continuous manner is the impracticability of what is called perpetual motion of the second kind/ that is, the utilization of the vast stores of energy in the ocean and in the earth. There is nothing contrary to the first law of thermodynamics in this concept, but the fact that it has not been found feasible provides support for the second law. The ocean, for example, may be regarded as a heat reservoir of constant temperature, and the law states that it is not possible to convert the heat continuously into work without producing changes elsewhere. 

The second law in this form denies the possibility of what has sometimes been called perpetual motion of the second kind, just as the first law denies that of the first kind, which is generation of work from nothing at all. 

This hypothetical process is called perpetual motion of the second kind. ... 

The Second Law states that Entropy is a state function. The purpose of the second law is to obviate perpetual motion of the 2nd kind i.e. heat cannot be converted to work with 100% efficiency. The differential form of the Second Law is... 

Perpetual motion of the third kind. A form of motion that continues indefinitely but without doing any useful work. An example is the random molecular motion in a substance. This type postulates the complete elimination of friction. A mechanism consisting of frictionless bearings maintained in a vacuum could turn indefinitely, once started, without contravening the first or second laws of thermodynamics, provided it did no external work. Experience indicates that on the macroscopic scale such a condition cannot be achieved. On the microscopic scale, however, a superconducting ring of wire will apparently sustain a perpetual current flow without the application of an external force. This could be considered a form of... 

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... 

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. 

Even in its original form the theorem deals with chemical reactions and changes of state, that is to say, with the most important natural phenomena accompanied by evolution or absorption of heat. It is therefore natural to suspect that the heat theorem, like the two law s of thermodynamics, has its origin in the nature of heat itself. The laws of thermodynamics, as was shown in Chapters III. and V., could be traced back to the results of our everyday experience (impossibility of perpetual motion of the first and second kinds). This simple method of derivation fails in the case of the new theorem because temperatures in the neighbourhood of the absolute zero can never be the immediate objects of experience. They can only be reached by refined experimental methods. For this reason Nernst s theorem can never be susceptible of direct experimental proof, and can only be tested by its consequences. We can deduce the theorem, however, from a more general principle regarding the nature of heat and the properties of the thermodynamic functions. 

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. 

In effect this theorem denies the existence of a perpetual motion machine of the second kind (PMM2), namely, a device acting as a "Maxwellian demon."... 

Laws may be also presented as classical statements about the impossibility of the perpetual motion of the first and second kind. 

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... 

Figure 3.5 Perpetual motion machine of the second kind, which according to the Second Law is impossible. The existence of such a machine would violate inequalities (3.3.7) and (3.3.8)...

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. 

Show the equivalence between a perpetual motion machine of the second kind and Carnot s theorem. 

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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