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A P-V diagram question

  1. Apr 26, 2017 #1
    When a gas in a closed system is compressed, should the graph always be non-linear? If T is constant ie if the process isothermal it is clear that it should be so but I am not very sure that if the graph can be horizontal. If T decreases might not it be horizontal?


    Thank you.
  2. jcsd
  3. Apr 26, 2017 #2
    Unless some other constitutive equation is specified, I'd be inclined to assume that the Idea Gas Law applies. Thus,
    P * V = N * R * T
    This will enable you to express P(V) and thus calculate the work done.
  4. Apr 26, 2017 #3
    Yes we can calculate the work done but I especially ask for the shape of the curve.

    Thank you.
  5. Apr 26, 2017 #4
    Solve the equation for P and you have the shape of the curve.
  6. Apr 26, 2017 #5
    But such a compression process is polytropic so the equation is also might be PVn=C and this is where I am confused.

    Thank you.
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