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Homework Help: Entropy - Maxwell Relations

  1. Nov 20, 2008 #1
    Hey guys.

    Right, I have been studying the Maxwell thermodynaic relations. But I have come across entropy as

    dS = (bS/bT)_P(dT) + (bS/bP)_T(dP)

    where b is the partial differential symbol.

    I dont understand where this comes from, which suggests S(T,P). I cant find a derivation of this.

    Could you help?
     
  2. jcsd
  3. Nov 20, 2008 #2
    It's nothing really to derive. Physically, I mean.
    For any function of two variables, the general formula for differentiation looks like this.
    I mean, for f(x,y)
    df=(bf/bx)dx+(bf/by)dy.

    As for why S(p,T), you can use any two independent variables as "dependent variables".
     
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