The Four Laws of Thermodynamics

The Four laws in their original state can be found at the end of this Article.
2.0 Four Thermodynamic Rules Always Obeyed
The clarification developed in the remainder of this paper obeys four ironclad rules:

2.1 Energy is conserved. Conservation of energy (the first law of thermodynamics) prohibits the efficiency of a system from exceeding 100%. Thus, the energy inputs to a working system must equal the sum of (i) the system’s useful work output and (ii) the system’s non-useful losses. Useful work output is the useful change of the form of energy. Non-useful losses are those that require work that does not produce a useful result. Obviously no system can change the form of energy that is not present and thus not available to be transduced! That is, the best a perfect, 100% efficient, system can do is to process all of its input energy into useful work with no losses whatsoever. But most real systems inevitably have some losses — even significant losses; they do not transduce 100% of the input energy into the desired new form. Thus the efficiency of any positive energy working system with losses is always less than 100%.

2.2 If no usable energy is input from the environment, the useful output of a system with any losses is less than the operator’s input, so its COP < 1.0. Nevertheless, the efficiency of such a system continues to be less than 100%.

2.3 A system can exhibit COP > 1.0 if it receives sufficient excess energy from its external environment — whether or not the operator inputs anything. Such a system’s efficiency is still less than 100% — even appreciably less. An example is the common home heat pump. Its overall efficiency is about 50%, and it wastes about half of the total input energy (supplied by the operator and the environment) in losses. However, the heat pump receives so much excess heat energy from the environment that it still outputs substantially more useful work than the input that the operator furnished. Indeed, even though a heat pump has an efficiency of ε = 50%, its nominal COP = 3.0 to 4.0.

2.4 A working system can exhibit COP = ∞ if it freely receives all its energy input from the environment and none from the operator. This is true even though the efficiency (the proportion of the total energy input that is usefully transduced) is always less than 100% and indeed may be quite low. A solar cell array power system, e.g., usually has an efficiency of only about ε = 20%. However, the operator input is zero and all the energy is input freely by the environment, so the system COP = ∞.

  • Zeroth law of thermodynamics: If two systems are in thermal equilibrium with a third, they are also in thermal equilibrium with each other.This statement implies that thermal equilibrium is an equivalence relation on the set of thermodynamic systems under consideration. Systems are said to be in equilibrium if the small, random exchanges between them (eg. Brownian motion) do not lead to a net change in energy. This law is tacitly assumed in every measurement of temperature. Thus, if one seeks to decide if two bodies are at the same temperature, it is not necessary to bring them into contact and measure any changes of their observable properties in time.[19]The law provides a fundamental definition of temperature and justification for the construction of practical thermometers.It is interesting to note that the zeroth law was not initially recognized as a law. The need to for the zeroth law was not initially realized, so the first, second, and third laws were explicitly stated and found common acceptance in the physics community first. Once the importance of the zeroth law was realized, it was impracticable to renumber the other laws, hence the zeroth. 
  • First law of thermodynamics: The internal energy of an isolated system is constant.The first law of thermodynamics is an expression of the principle of conservation of energy. It states that energy can be transformed (changed from one form to another), but cannot be created or destroyed.[20]The first law is usually formulated by saying that the change in the internal energy of a closed thermodynamic system is equal to the difference between the of heat supplied to the system and the amount of work done by the system on its surroundings. It is important to note that internal energy is a state of the system (see Thermodynamic state) whereas heat and work modify the state of the system. In other words, a specific internal energy of a system may be achieved by any combination of heat and work; the manner by which a system achieves a specific internal energy is path independent. 
  • Second law of thermodynamics: Heat cannot spontaneously flow from a colder location to a hotter location.The second law of thermodynamics is an expression of the universal principle of decay observable in nature. The second law is an observation of the fact that over time, differences in temperature, pressure, and chemical potential tend to even out in a physical system that is isolated from the outside world. Entropy is a measure of how much this evening-out process has progressed. The entropy of an isolated system which is not in equilibrium will tend to increase over time, approaching a maximum value at equilibrium.In classical thermodynamics, the second law is a basic postulate applicable to any system involving heat energy transfer; in statistical thermodynamics, the second law is a consequence of the assumed randomness of molecular chaos. There are many versions of the second law, but they all have the same effect, which is to explain the phenomenon of irreversibility in nature. 
  • Third law of thermodynamics: As a system approaches absolute zero, all processes cease and the entropy of the system approaches a minimum value.The third law of thermodynamics is a statistical law of nature regarding entropy and the impossibility of reaching absolute zero of temperature. This law provides an absolute reference point for the determination of entropy. The entropy determined relative to this point is the absolute entropy. Alternate definitions are, “the entropy of all systems and of all states of a system is smallest at absolute zero,” or equivalently “it is impossible to reach the absolute zero of temperature by any finite number of processes”.Absolute zero, at which all activity would stop if it were possible to happen, is -273.15 °C (degrees Celsius), or -459.67 °F (degrees Fahrenheit) or 0 K (kelvin).
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