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Homework Help: I need some help on RC circuit

  1. Mar 22, 2013 #1
    1. The problem statement, all variables and given/known data

    I'm trying to use the equation for charging capacitor that's discharging, and I can't get the answer right. On the calculator it keeps showing as 1.

    2. Relevant equations

    I(t) = -(1.96) [e^((-9.0*10^(-6)) / (1300)(2.0*10^(-9)))]

    3. The attempt at a solution

    My problem is that the exponential part keeps coming out as the value 1 when I input it into the calculator. I need help on solving the exponential part.
    Last edited by a moderator: Mar 22, 2013
  2. jcsd
  3. Mar 22, 2013 #2
    Is the equation $$ -1.96 \exp{\frac {-9.0*10^{-6}}{1300*2.0*10^{-9}}} $$ or is it $$ -1.96 \exp({\frac {-9.0*10^{-6}}{1300}2.0*10^{-9}}) $$?
  4. Mar 22, 2013 #3
    the first one... e^(-t/RC)
  5. Mar 22, 2013 #4
    The way you typed it, however, it will be interpreted as #2. You need additional brackets to enforce #1, OR you must use the division operation twice.
  6. Mar 22, 2013 #5
    oh. thank you for the clarity. it works.:smile::rofl:
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