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Cp and Cv

  1. Feb 6, 2006 #1
    Aren't we doing some work to prevent the gas from expanding if we maintain the constant volume. So shouldn't molar specific heat at constant pressure be equal to constant volume?
  2. jcsd
  3. Feb 6, 2006 #2
    You don't do work with a change in pressure, but rather a change in volume:

    dW = PdV

    Since work is done in the constant pressure case but not the constant volume one, Cp and Cv are different.
  4. Feb 6, 2006 #3

    Meir Achuz

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    The force preventing the expansion is stationary. Only a moving force can do work.
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