Entropy and The Second Law

The Finer Points of Heat

 By 1852, Thomson had come to believe that heat could be both transformed into work, as described by Joule’s theory, and free flowing to produce no work at all, as described by Fourier’s theory. In the latter, heat was simply dissipated, but not lost in accordance with the first law. Moreover, he distinguished between high quality and low quality energy and insisted that the universal tendency for energy is to dissipate as heat, making it unavailable for work. But Thomson wasn’t the only one thinking about the finer points of heat … so was Clausius.
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The Thermodynamic Origins of Entropy: Carnot and The Heat Engine

Carnot, Caloric Theory and The Heat Engine

In 1823 when Sadi Carnot (1796–1832) began this task, less than thirty years had passed since Rumford’s cannon-boring experiments led him to declare “heat is motion”. And although this should have been the end of caloric theory, it and its principle of heat (caloric) conservation were mostly undaunted. Further, a more complete understanding of energy would have to wait for some thirty years for the first law to be established.

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Carnot the Outsider

During his formal education Sadi Carnot (1796-1832) was literally surrounded by renowned physicist, chemists and mathematicians on the faculty. However, Carnot was never a member of this distinguished group, and did his most important work (as a founder of modern day thermodynamics) as an outsider.

Clapeyron’s Reformulation of Carnot’s Work

In 1834 Émile Clapeyron (1799-1864), a former classmate of Carnot’s, published a paper in the Journal de l’École Polytechnique. Here he reformulated Carnot’s work using clear concise mathematics and a new graphical presentation for Carnot’s reversible heat engine (still taught today to every chemistry major taking a good physical chemistry class) that finally brought Carnot’s work to the attention of engineers, chemists and physicists.