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Homework Help: Work to compress a gas (constant external pressure)

  1. Oct 6, 2008 #1
    What is the work to compress a gas under constant external pressure?
    It seems that it is supposed to be w = -P(ext)delta(V)
    This equation is certainly true for expansion of a gas, is it also true for compression?
    So if we have two gases, same initial conditions, same delta(v) under compression. One is compressed by 10 atm and the other by 5 atm. They end at the same volume, but have different work done on them?
    The observational difference I can see is that the 10 atm compression would occur faster than the 5 atm compression. Is the work really a factor of 2 different?
    Or, is work really dependent upon the lower of internal and external pressures, and the books talk about expansion more than compression?
  2. jcsd
  3. Oct 6, 2008 #2


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    Science Advisor

    Yes, it's the same concept, only the sign of delta(V) changes depending on the situation.
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