Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

DU=TdS-PdV proof?

  1. Sep 29, 2006 #1
    When proving the equation,

    why is dw= PdV not dw= PdV +vdP?
  2. jcsd
  3. Sep 29, 2006 #2
    I think it is as you wrote, but don't quote me. I'm at school and dont have my book infront of me.
  4. Sep 29, 2006 #3

    Andrew Mason

    User Avatar
    Science Advisor
    Homework Helper

    Work (force x distance) is done only if the pressure (force/area) acts over some change in volume (area x distance moved). If there is no change in volume, the force does not act over any distance - ie. the pressure just builds up but does not move anything (ie. it just increases internal energy). So, VdP is part of the internal energy of the gas, not the work done by the gas.

  5. Sep 30, 2006 #4
    thank you!
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook