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Is this against Kelvin-Planck statement?

  1. Jul 6, 2015 #1

    pitbull

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    Gold Member

    1. The problem statement, all variables and given/known data
    An ideal gas expands isothermally in contact with a heat source. ∆U is zero in this case because it is an ideal gas and T=constant. Is this against Kelvin-Planck statement?

    2. Relevant equations
    pv=nRT
    dW=-pdV
    Kelvin-Planck statement: There is no proccess whose only result is the full transformation of heat into work.

    3. The attempt at a solution
    My guess is, ∆U=Q+W=0, therefore
    Q=integral(pdv)=nRTlog(Vfinal/Vinitial)>0
    W=-nRTlog(Vfinal/Vinitial)
    So all the heat that the gas absorbs turns into work. Therefore, this is against K-P statement, but I have a feeling that I am wrong. Can you guys help me?
     
  2. jcsd
  3. Jul 6, 2015 #2

    TSny

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