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: Constant thermodynamic potentials examples

  1. Jun 8, 2010 #1
    1. The problem statement, all variables and given/known data

    Specify at least two ( physical or chemical), real world, processes for each of this cases:

    a) Internal energy is constant
    b) Entalpy is constant
    c) Gibbs free energy is constant
    d) Helmholtz free energy is constant

    2. Relevant equations

    a) dU = TdS - pDV = 0
    b) dH = TdS + VdP = 0
    c) dG = dH - tdS = 0, or dG =vDp -SdT = 0 ???
    d) dF = -(pdV + SdT ) = 0

    3. The attempt at a solution

    b) Joulle-Thompson effekt

    ...and this is all what I found...

    Thanks for any help !
    Last edited: Jun 8, 2010
  2. jcsd
  3. Jun 8, 2010 #2


    User Avatar
    Science Advisor
    Homework Helper
    Gold Member

    It's not going to help you learn if people just provide the examples for you, so let's try this tack: what's the physical interpretation of [itex]dS=0[/itex]? How about [itex]dP=0[/itex], and the others? Can you brainstorm some cases where these restrictions apply? For example, which state variables are constant when an exposed solid melts to form a liquid?
  4. Jun 8, 2010 #3
    Maybe it is true, but I think that knowing real world examples help me to better understand thermodynamics. Than, I can compare "mathematics" with real world.
  5. Jun 8, 2010 #4
    This stand for constant gibbs, am I right ?
  6. Jun 8, 2010 #5


    User Avatar
    Science Advisor
    Homework Helper
    Gold Member

    Sorry, we don't provide answers to homework-type questions. If you show your own effort, however, you'll likely get helpful comments.
  7. Jun 8, 2010 #6
    I'll try, thank you anyway
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook