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Homework Help: Adiabats versus Isotherms - Quick clarification

  1. Sep 21, 2011 #1
    1. The problem statement, all variables and given/known data
    I'm doing a problem about a cylinder containing a gas. A piston attached to the cylinder is
    1) pushed in slowly
    2) pushed in quickly

    Before I continue with the problem, I want to make sure that my assumptions are correct.

    I am going to model 1) as an isothermal process. It goes slowly enough that the system's temperature stays the same as it has time to transfer heat from the outside.

    I'll model 2) as an adiabatic process. It's fast enough that no heat is transferred between the system and the surroundings.

    2. Relevant equations

    3. The attempt at a solution
    Is my understanding of this correct? I am not entirely clear on isothermal vs adiabatic processes...
  2. jcsd
  3. Sep 21, 2011 #2


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    Homework Helper

    It sounds like you understand the difference between isothermal and adiabatic processes.

    Does the problem specify that the system (cylinder) is surrounded by a fixed-temperature heat reservoir? If not, you have to think more carefully about the heat transfer in (1).
  4. Sep 21, 2011 #3
    My thermal physics professor has put it into those terms often, that 'slowly' indirectly means 'isotherm' and 'quickly' indirectly means adiabat, for precisely the reasons you said. So I believe you are correct in assuming that, given no other specific information but what you posted. If the question were more in-depth with more details, it would not be a good idea to jump to those conclusions before analyzing the entire situation. But a vague, more general question, I believe that would be perfectly reasonable to assume.

    [I know I'm just a student myself and not an 'expert' but I thought it wouldn't hurt to share.]
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