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Homework Help: Carnot cycle, heat and monatomic ideal gas

  1. Mar 5, 2004 #1
    Hi, I would appreciate any help with this:

    A monatomic ideal gas is used as the working substance for
    the Carnot cycle. Processes A => B and C => D
    are isothermal, while processes B => C and D => A are adiabatic.
    During process A => B, there are 400 J of work done by the gas on
    the surroundings. How much heat is expelled by the gas during process C => D?

    So I'm completely stuck, all I know is that it's less than 400 J, obviously.
    There's a picture of the corresponding PV graph actually at http://www.compadre.org/psrc/evals/Physics_Bowl_2003.pdf (page 12).

    Thanks for any help!!
  2. jcsd
  3. Mar 7, 2004 #2
  4. Mar 7, 2004 #3
    I'm not sure about this explanation, but whatever. You know that the carnot cycle runs at perfect efficiency ie. 1-(Ql/Qh) and you know that efficiency of the carnot cycle is also 1-(Tl/Th). I get 100 J.
  5. Mar 8, 2004 #4
    Thanks! I actually figured it out later with the adiabatic equation (PV^gamma is constant) but your way is much more elegant.
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