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Homework Help: Thermo 1st Law piston problem

  1. Sep 22, 2016 #1
    1. The problem statement, all variables and given/known data
    Air in an insulated cylinder is separated by a piston into two equal valves. When the pin is
    removed, the system comes to a new equilibrium position. There is friction between the piston and
    the cylinder walls but friction does not influence the mechanical equilibrium condition (at the final
    state, the pressures are equal). For case (1) the piston
    is heat conducting.
    Estimate the upper and
    lower limits for the temperature in chamber A and B

    For Chamber A given: T1=300k, P1= 2bar
    For Chamber B given: T1=300k P1=1bar
    **Picture attatched**

    2. Relevant equations

    3. The attempt at a solution
    Considering one side at a time this doesn't seem like a constant volume, pressure or adiabatic problem.
    From pv=nRt the amount of moles in Chamber A are twice that in chamber B.
    -Given that the piston is heat conducting does this mean that the temperature will be the same for chamber A and B at equilibrium, why would there be two different temperature limits? Even then, it feels like there's missing information to solve the problem, PVϒ = Constant doesn't apply here I don't think since the process is not adiabatic

    Attached Files:

  2. jcsd
  3. Sep 23, 2016 #2
    Term adiabatic is for process. This process is not adiabatic as you guess correctly. Piston is conducting and friction exists between piston and cylinder walls does not make it isothermal also. Internal energy is not conserved. Pressure becomes same at equilibrium but the temperature which is the measure of average internal energy per molecule could be different in two chambers as the partition is perhaps not conducting. At present I can say only this much.
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