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Homework Help: PV diagram & transfer of heat

  1. Dec 9, 2007 #1

    sun

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    1. The problem statement, all variables and given/known data

    A gas is taken through the cyclic process described by Figure P12.16.

    http://www.webassign.net/sf/p12_16.gif

    (a) Find the net energy transferred to the system by heat during one complete cycle.

    (b) If the cycle is reversed -- that is, the process follows the path ACBA -- what is the net energy transferred by heat per cycle?

    PV=[nR]T
    [nR]=PV/T
    W=-P(deltaV)


    What I have done so far:


    ______P(kPa)--------V(m^3)------------U(J)--------------[nR]
    A_____2x10^3--------- 6 --------------18x10^3 ----------43.96
    B_____8x10^3----------10-------------120x10^3---------293.04
    C_____2x10^3---------10---------------30x10^3-----------73.30



    _________W(J)___________Q(J)___________deltaU(J)
    A->B_____-8,000________110,000_________102,000
    B->C______0__________-90,000___________-90,000
    C->A_____8,000_________20,000__________-12,000

    Wouldn't the net energy transfered to the system by heat be the sum of the Q values? I get 40,000J for this, but it seems to be wrong. Suggestions would be greatly appreciated.


    thanks
     
    Last edited: Dec 9, 2007
  2. jcsd
  3. Dec 9, 2007 #2

    sun

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    I know its a bit tedious, but any suggestions?
     
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