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Thermodynamics

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The first established principle of thermodynamics (which eventually became the Second Law) was formulated by Sadi Carnot in 1824. By 1860, as found in the works of those such as Rudolf Clausius and William Thomson, there were two established "principles" of thermodynamics, the first principle and the second principle. As the years passed, these principles turned into "laws." By 1873, for example, thermodynamicist Josiah Willard Gibbs, in his “Graphical Methods in the Thermodynamics of Fluids”, clearly stated that there were two absolute laws of thermodynamics, a first law and a second law.

Over the last 80 years or so, occasionally, various writers have suggested adding Laws, but none of them have been widely accepted. …show more content…

At present, it is unquestioned.

[edit] Second law

Main article: Second law of thermodynamics

The entropy of an isolated system not in equilibrium will tend to increase over time, approaching a maximum value at equilibrium.

In a simple manner, the second law states that "energy systems have a tendency to increase their entropy" rather than decrease it.

A pithy summation of the Second Law would be "You Can't Even Break Even".

A way of looking at the second law for non-scientists is to look at entropy as a measure of chaos. So, for example, a broken cup has less order and more chaos than an intact one. Likewise, solid crystals, the most organized form of matter, have very low entropy values; and gases, which are highly disorganized, have high entropy values.

The entropy of a thermally isolated macroscopic system never decreases (see Maxwell's demon). However, a microscopic system may exhibit fluctuations of entropy opposite to that dictated by the Second Law (see Fluctuation Theorem). In fact, the mathematical proof of the Fluctuation Theorem from time-reversible dynamics and the Axiom of Causality constitutes a proof of the Second Law. In a logical sense the Second Law thus ceases to be a "Law" of physics and instead becomes a theorem which is valid for large systems or long times.

The first and second law can be combined to yield the Fundamental Thermodynamic Relation:

dE = TdS - pdV\,

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