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Homework Help: RC Circuits - R vs. tau

  1. Nov 17, 2007 #1
    1. The problem statement, all variables and given/known data

    In an RC circuit, should a graph of R vs. tau necessarily go through the origin? What does a non-zero intercept indicate?

    2. Relevant equations

    3. The attempt at a solution

    My graphs look like they go through the origin, and from the equation tau = RC, I would expect that when R is zero, tau is also necessarily zero. However, from the definition of tau as the time necessary for the charge on a capacitor to go from 0 to 63.2% of the max charge, it seems to me that tau can never actually be zero. Also, because the wires themselves have some degree of resistance, R seems like it would never actually be zero either. I'm not sure which idea to go with.

    Thanks for your help!
  2. jcsd
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