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Homework Help: Resistance and Capacitators - check my work.

  1. Feb 18, 2010 #1
    A heart pacemaker is designed to operate at 71 beats/min using a 8.5 microF capacitor in a simple RC circuit.

    What value of resistance should be used if the pacemaker is to fire (capacitor discharge) when the voltage reaches 69% of maximum?

    Here's what I've done (but my answer was wrong):

    R= t / (C*ln[v0 / v])

    with t = 1.183 beats/sec
    C = 8.5 x 10-6F
    v0/v = 0.69

    R = -3.8 x 108 ohms

    Where did I go wrong?
  2. jcsd
  3. Feb 18, 2010 #2


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    Science Advisor
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    Hi vucollegeguy! :smile:
    I'm not an expert on capacitors :redface:

    but shouldn't t be a time ? :confused:
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