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Evaluation of work in thermodynamics

  1. Sep 8, 2015 #1
    Inside a cylinder with a sliding piston, n mole of monoatomic ideal gas at temperature TA occupy a volume VA at pressure PA, in equilibrium. The piston is expanded very slowly, turning the pressure in such a way that the product V⋅P2 remains constant till the volume VB .

    I have to evaluate the work in the transformation from A to B:
    VB = 4 VA
    PA and VA are known

    wAB = ∫ P⋅dV =

    My question is:
    - Which value of Pressure shall I insert instead of P considering the fact that it isn't constant during the transformation?
  2. jcsd
  3. Sep 8, 2015 #2
    If VP2 remains constant, it must be equal to VP2 in state A. Can you write an equation to express this in terms of PA and VA?

  4. Sep 8, 2015 #3

    Doc Al

    User Avatar

    Staff: Mentor

    Express P as a function of V.
  5. Sep 8, 2015 #4
    and then I substitute in the integral:
    ∫ (VB½⋅PB)/VA½ dV

    is it ?
  6. Sep 8, 2015 #5
    Not exactly. VP2=VAPA2

    Solve for P and then integrate PdV between VA and VB.
  7. Sep 8, 2015 #6
    Aw ok! now i get it.
    Thank you very much for your time. Very helpful.
    Have a nice day : )
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