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Did Carnot use caloric theory .

  1. Nov 7, 2012 #1
    Did Carnot use "caloric theory".

    Wikipedia asserts the following:

    "Though Carnot had developed a compelling analysis of a generalised heat engine, he had employed the clumsy and already unfashionable caloric theory."
    http://en.wikipedia.org/wiki/Benoît_Paul_Émile_Clapeyron

    Feynman (FLP Vol I, 44-1) asserts: "But it turned out that Clapeyron assumed, not the conservation of energy in general, but that heat was conserved according to caloric theory, which was later shown to be false. So it has often been said that Carnot's logic was wrong. But his logice was quite correct. Only Clapeyron's simplified version, that everybody read, was incorrect."

    I note that Feynman doesn't explicitly state that Carnot didn't use caloric theory, but he pretty clearly contradicts what Wikipedia asserts. So what's the real history here? Who did or did not use caloric theory?
     
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  3. Nov 8, 2012 #2

    Andy Resnick

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    Re: Did Carnot use "caloric theory".

    The most complete source for information like this is Truesdell's "The Tragicomical History of Thermodynamics 1822-1854". To summarize:

    Laplace invented the caloric theory: heat is never created or destroyed. Carnot did indeed use this theory, for example when he wrote "Thus the production of motive power is due... not to any real consumption of caloric, but to its transport from a warm body to a cold body..."

    However, Carnot's result- the analysis of a cyclic process- does not make use of caloric theory. As Truesdell writes: "The spectators ... will see that the protagonist while seeming to smelt lead has cast a gold ingot."

    One source of confusion is the distinction between infinitesimal differences in temperature and finite differences in temperature during a cyclic process. The Carnot-Clapyron theorem for the former does not require heat to be conserved while it does for the latter. Thus, his most general result does not rest upon caloric theory.
     
  4. Nov 8, 2012 #3
    Re: Did Carnot use "caloric theory".

    Thanks. That seems like a reliable answer.

    Now the other side of the issue: did Clapeyron rely on caloric theory for his conclusions?
     
  5. Nov 9, 2012 #4

    Andy Resnick

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    Re: Did Carnot use "caloric theory".

    That's tough to say- Clapeyron primarily translated Carnot's work into a mathematical form, as opposed to generating new results. Consequently, although the argument is couched in terms of caloric theory, the results are independent of caloric theory.
     
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