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Homework Help: How to visualize entropy in thermodynamics

  1. Nov 10, 2006 #1
    entropy is the measure of disorder....but i jsut cannot visualize it in a practical standpoint...i mean...the disorder taking place with soo many particles when heated and yet all i know is that s=q/t....can anyone explain this concept better to me?

    one more question...how does one prove using statistical mechanics that
    s=(boltzmann's constant)lnw....were w is the number of macrostates...

    i was tryng to do calculus based entropy probelms...but can do them in refrence to s=(boltzmann's constant)lnw, by counting the number of macrostates available??

    and is it possible to find th number of macrostates by equating (boltzmann's constant)lnw=q/t....is this a very large number?
  2. jcsd
  3. Nov 10, 2006 #2
    Entropy of a composite system is given by:
    S* = SA + SA'-----(1)
    Number of accessible states to A* is:
    W* = WAWA'------(2)

    S*,SA, SA' are entropies of composite system A*, A and A' respectively(A* composed of A and A').
    The entropy is a "state" function.
    For (1) & (2) to hold good simultaneously, what should be the nature of this function?
  4. Nov 10, 2006 #3


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    W in S=klnW is the number of microstates.

    I was indtroduced to entropy through S=klnW as the definition, therefore it's not provable. What definition of S do you use??
  5. Nov 10, 2006 #4

    Andrew Mason

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    Use the thermodynamic definition of entropy and forget about the concept of disorder: dS = dQ/T

  6. Nov 10, 2006 #5
    You'll need to use the definition of temperature [tex]\frac{1}{k_{B}T} = \frac{\partial\ln\Omega}{\partial U}[/tex] as well.
  7. Nov 10, 2006 #6
    ...though you might want to show where that comes from, it might be kinda easy otherwise...
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