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Homework Help: Comparison b/w work done in adiabatic & isothermal processes

  1. Apr 22, 2012 #1
    1. The problem statement, all variables and given/known data

    In the graph attached, why is isothermal graph line higher than adiabatic one??

    2. Relevant equations

    3. The attempt at a solution
    At first, i had thought that work done in an isothermal process is greater than in an adiabatic process....but for comparison we would need same initial and final states (P & V) , wouldn't we?

    Attached Files:

  2. jcsd
  3. Apr 22, 2012 #2

    I like Serena

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    The area under the graph is the work done by the gas (W=∫PdV)

    You can compare those areas and see that in an isothermal process the work done is indeed higher than in an adiabatic process.

    For a proper comparison you would need indeed the same final P&V.
    So introduce an extra isochoric (constant volume) process step (a vertical line in your diagram) and presto!
  4. Apr 22, 2012 #3
    i know that............. my doubt was that P & V which are describing the state should be same(initial and final), then we can compare the work done through 2 ways: adiabatic & isothermal
    but i have got it..the graph simply indicates that if we expand a gas and do it isothermally it would require more work to be done
    thanks :)
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