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Homework Help: Thermodynamics Problem

  1. Jun 21, 2009 #1
    1. The problem statement, all variables and given/known data
    A cylinder contains 2 moles of gas initially at state A it has a volume of 1*10^-2m^3 and a pressure of 4*10^5. It the is brought isobarically to state B where the new volume is 2*10^-2. It is then brought at a constant volume to state C where the temperature is the same as in step A. It is then finally brought isothermally back to state A.
    a)Is the net work done during the complete cycle positive, negative, or zero?
    b)Is this device a heat engine or a refrigerator?

    2. Relevant equations

    3. The attempt at a solution
    I've already got answers but I'm not positive.

    Part a
    Positive b/c the work done by the gas going from A to B is greater than the work done on the gas going from C to A. This is seen through A bring at a higher pressure than C while they have the same differential in volume. No work is done from B to C.

    Part b
    I said it is a heat engine for two reasons. First the heat of the system increases and second b/c the work done during the cycle is positive. In a refrigerator work more work must be done on the system for the cold air to move to the hot region.
  2. jcsd
  3. Jun 22, 2009 #2
    Everything seems to check out here.

    You should probably make a P-V graph if you want to show your answers better.
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