Machines perpetual motion

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... 

In free molecular flow, if gaseous conductance were not independent of the flow direction, a perpetual-motion machine could be constmcted by connecting two large volumes by a pair of identical ducts having a turbine in front of one of the ducts. A duct that has asymmetricaUy shaped grooves on its waU surface could alter the probabUity of molecular passage in such a way that for a tube of equal entrance and exit areas, the probabUity of passage would be made directional. 

Thermodynamic considerations demand that the energy necessary for biosynthesis of any substance exceed the energy available from its catabolism. Otherwise, organisms could achieve the status of perpetual motion machines A few molecules of substrate whose catabolism yielded more ATP than required for its resynthesis would allow the cell to cycle this substance and harvest an endless supply of energy. 

John W. Keely (lS27-1898j sealed to what he claimed was Ihe first perpetual motion machine until after he died. (Corbis Corporation)... 

To prove that a particular design of a perpetual motion machine will not work can be vei y time consuming, and the predictable negative result has never been worth the effort. Therefore, the U.S. Patent Office has a policy to not examine applications covering perpetual motion machines unless the applicant furnishes a working model. 

The nonexistence of perpetual motion machines, despite centuries of effort to design them, has been used to support the law of consciwation of energy. This law is based, however, not on this negative result, but on all the experiments performed to date in which energy is carefully accounted for. It has never been observed to fail. This law is, therefore, a good basis from which to analyze perpetual motion machines. It clearly states that the goal of getting... 

The consideration of the simple pendulum illustrates the basic problem behind devising a perpetual motion machine. The problem is the fact that energy exists in several forms and is transformed from one form to the other, especially when motion is involved. Even if friction is eliminated, there arc still the electromagnetic radiation and gravitational inter-... 

Their data translated into a power output of lOOW/kg. Where was the power coming from Was this finally an illimitable source of energy, nature s own perpetual-motion machine It was here that Einstein, in a concise phrase, carried the argument to its limit. In his own derivation of = mcr in 1905, five years after Poincare s observation, he remarked that any body emitting radiation should lose weight. 

George earned the prestigious position of brakesman at the Dolly Pit colliery, responsible for the engine used for hauling coal out of the mines. He was married in 1802. During that year he made an unsuccessful attempt to build a perpetual motion machine. But he did gain respect in the community as an accomplished clock-mender. 

The predictions of the Third Law have been verified in a sufficiently large number of cases that experimental attempts to reach absolute zero are now placed in the same class as attempts to devise perpetual motion machines — which is to say there are much more productive ways to spend one s time. Much experimental work is carried out. however, at very low temperatures, because the behavior of matter under these conditions has produced many surprises and led to the uncovering of a great deal of new knowledge and the development of useful new devices, such as superconducting magnets.cc... 

The rationale is like settling the issue around perpetual motion machines by the second law of thermodynamics rather than examine each proposed device independently. 

Perpetual motion machines seem to be a favourite project for inventors who do not understand the second law of thermodynamics. Design a simple machine that, once started, would recycle energy and, according to the first law of thermodynamics, should carry on forever. Why does the second law of thermodynamics rule out the possibility of ever making a perpetual motion machine ... 

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

First Law of Thermodynamics. The total amount of energy within a closed system is constant (/.e., the total energy of the system is conserved). Mathematically, this can be expressed as AU = q + w where At/ is the change in internal energy, q is the heat transferred to the system, and w is the work done on the system (or, dU = dq + dvr). Internal energy is a state function (/.c., it is dependent only on the initial and final states and not on the path between those states). In addition, the validity of the first law means that perpetual motion machines are impossible. See Conservation of Energy... 

Consequence of First Law It is impossible to construct a machine ( perpetual motion machine of the first kind ) that produces useful work in a cyclic process without a compensating change in the surroundings. 

It was the principal genius of J. W. Gibbs (Sidebar 5.1) to recognize how the Clausius statement could be recast in a form that made reference only to the analytical properties of individual equilibrium states. The essence of the Clausius statement is that an isolated system, in evolving toward a state of thermodynamic equilibrium, undergoes a steady increase in the value of the entropy function. Gibbs recognized that, as a consequence of this increase, the entropy function in the eventual equilibrium state must have the character of a mathematical maximum. As a consequence, this extremal character of the entropy function makes possible an analytical characterization of the second law, expressible entirely in terms of state properties of the individual equilibrium state, without reference to cycles, processes, perpetual motion machines, and the like. 

Are any of the following devices perpetual motion machines of the first or second kinds Which kind are they and why ... 

When heat is transformed into any other form of energy, or when other forms of energy are transformed into heat, the total amount of energy (heat plus other forms) in the system is constant. This is known as the first law of thermodynamics, i.e., the conservation of energy. To express it another way it is in no way possible either by mechanical, thermal, chemical, or other means, to obtain a perpetual motion machine i.e., one that creates its own energy. 

Efficiency, the word crops up virtually every time superconductivity is mentioned, and it is not difficult to see why. Efficiency, after all, is simply doing more with less effort, and when a superconductor carries electricity with no resistance and essentially no loss—and, theoretically, forever without any decrease in flow—that s efficiency of a most enviable kind. And although the transition from conventional superconductors cooled with liquid helium to the new high-temperature ceramics cooled with liquid nitrogen would not improve superconductivity—how, after all, can one make a perpetual motion machine more perpetual —it would dramatically lower costs, simplify refrigeration systems, and improve the reliability of just about everything electric in which the ceramics are used. 

Throughout our discussion of superconductivity, we have frequently likened the phenomenon to a perpetual motion machine because of the peculiar ability of a superconductor to allow current to flow indefinitely through it. In numerous tests, electricity has been shot through and around a superconducting loop for years, and scientists, using extremely sensitive instruments, have been unable to measure any drop in the current as small as 1 part in over 100,000,000,000. 

Discuss the relevance of the Law of Conservation of Energy to the operation of perpetual motion machines. 

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. 

If the first law were false, one could construct a perpetual motion machine by starting with an isolated system, removing it from isolation, and letting it do work on the surroundings. It could then be placed in isolation again, and its internal energy allowed to return to the initial value. This feat has never been accomplished despite many attempts. 

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