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Homework Help: Capacity of a Capacitor

  1. Feb 16, 2006 #1
    This is for a lab I have done and I am stuck on this,

    Question : Plot a curve of In (1 - V/Vo) vs time and calculate C from the slope of the line.

    Initial equation = V = Vo(1-e^-t/RC)
    Calculated Linear Equation : In (1 - V/Vo) = -t/RC
    Therefore from y = mx + b = m = -t/RC (i think)
    Then, C = -t/Rm

    m = -72.673
    R = 10 000 ohms
    C = what we are looking for
    -t = ????? do i use any of my times

    Also, C (accepted value) = 6000x10^-6 Farad
    Therefore, answer should be near this.

    Please help me out! I'm totally stumped. Thank you.
    Last edited: Feb 16, 2006
  2. jcsd
  3. Feb 16, 2006 #2
    Can anybody help?
  4. Feb 16, 2006 #3
    i beleive i have a lead t = time constant but i dont know what that is...
  5. Feb 17, 2006 #4


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    Staff Emeritus
    Science Advisor
    Gold Member

    Yes you must plot all of your data. At each time, t, you measured some voltage, v,. Plot the points t, and

    [tex] \ln ( 1 - \frac v v_0 ) [/tex]

    where v is your measured values. You should get something linear, find the slope of the line.
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