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Setting up integration, thermodynamics

  1. Sep 19, 2010 #1
    I have a general problem with finding the right parts for integrations.

    For example, for an Isothermal expansion, both pressure and volume are changing. For some reason we call V=dv and relate P to V by the ideal gas law and integrate to get work:

    W= nRT ln (VF/ Vi)

    Now, could we do the same thing, and call work the integral of:

    W= [tex]\int[/tex]Vdp
    Which would lead to

    W= nRT ln (Pf/ Pi)



    If both quantities are changing? How do we know which to set as the differential, and which to relate in terms of the other variable?

    or why couldn't I do a double integral? first over the volume, then over the pressure?





    Also: Why does the LAtex code show up all messed up when I hit 'preview post'....?


    thanks
     
  2. jcsd
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