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Homework Help: Partition Function For a Single Molecule

  1. Aug 13, 2013 #1
    1. The problem statement, all variables and given/known data
    Polymers, such as rubberbands, are made of very long molecules, usually
    tangled up in a configuration that has lots of entropy. As a very crude
    example of a rubber band, consider a chain of N molecules which we call
    links, each of length l. Imagine that each link has only two possible states,
    pointing either left or right. If a link point to the right, it has energy −lF,
    where F > 0 is the force pulling on the rubber band. If a link points to the
    left, it has energy +lF. The end-to-end length of the rubber is
    L = (<NR> − <NL>)l ,
    where <NR> and <NL> are the average number of links that point to the right
    and to the left, respectively.
    (i) Write the partition function for a single link (molecule), Z1.

    3. The attempt at a solution
    Since I did this out in microsoft word I attached a screenshot of what I think is the solution - partition functions are not my strong point and I have an exam tomorrow where I believe a similar question will come up, so I just want to check if I have the correct answer.

    Last edited by a moderator: May 6, 2017
  2. jcsd
  3. Aug 13, 2013 #2


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    That looks right to me.
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