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Homework Help: Work in Adiabatic/ Isothermal and Piston

  1. Sep 29, 2011 #1
    1. The problem statement, all variables and given/known data

    Is work greater in adiabatic or isothermal process?

    A piston with oxygen has a final volume 1/4 the initial. The temperature is also 5 times greater. Determine pressure change, heat released or absorbed, and work done on or by gas.



    2. Relevant equations

    the work for adiabatic and isothermal. General w= -integral pdv, conservation of energy deltaV=Q+w

    3. The attempt at a solution

    I have derived the the expressions for work in both adiabatic and isotherm process from their integrals. ie:- Kln(vf/vi) and -k(vf1-gamma-vi1-gamma)/(1-gamma). But I'm not sure how to show that work in isothermal > adiabatic.

    For the second part I'm just not sure how to take into account both temperature and pressure, and I can't assume that it's adiabatic/isothermal in the beginning. Any ideas?

    Note: I did trying doing the double integral, dvdt....but i still only get an expression only.
     
    Last edited: Sep 29, 2011
  2. jcsd
  3. Sep 29, 2011 #2
    Consider a gas undergoing an isothermal and an adiabatic change both having the same change in volume and both starting from the same point on a PV diagram.
    Sketching the corresponding PV graphswill show which process has tha bigger work.
     
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