1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
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