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

Homework Help: Help with proof of thermodynamics equation!

  1. Apr 14, 2010 #1
    1. The problem statement, all variables and given/known data
    Suppose a thermodynamic system consists of a wire of length L under a tension T show that:
    (dF/dL)=T
    and
    (dF/dT)=-S
    (both are partial derivatives)


    2. Relevant equations
    F=U-TS
    H=U+PV
    G=U+PV-TS
    dU=TdS-pdV
    dF=-SdT-pdV
    dH=TdS+Vdp
    dG=-SdT+Vdp
    dQ=TdS
    dW=pdV


    I'm getting confused with the T for temperature and T for tension. Please explain to me how to do this as I have no idea about where I should begin.
    Thank You
    1. The problem statement, all variables and given/known data



    2. Relevant equations



    3. The attempt at a solution
     
  2. jcsd
  3. Apr 15, 2010 #2

    Mapes

    User Avatar
    Science Advisor
    Homework Helper
    Gold Member

    How about modifying the differential equation [itex]dF=-S\,dT-P\,dV[/itex] to incorporate work done by stretching the wire? Also, you can probably ignore [itex]P\,dV[/itex] work in this problem.
     
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook