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Homework Help: Current in Discharing Capacitor

  1. Apr 22, 2010 #1
    1. The problem statement, all variables and given/known data

    How do you express the current in a discharging capacitor.

    I know that I = dQ/dt,

    Qd = Q0e^(-t/RC)
    I = d/dt (Q0e^(-t/RC))
    = (Q/RC)e^(-t/RC)

    I am confused because taking the derivative of Q0e^(-t/RC)) I think should be
    (-Q/RC)e^(-t/RC) because the derivative of (-t/RC) is (-1/RC)

    Which solution is correct
    Thanks in advance
  2. jcsd
  3. Apr 23, 2010 #2
    Don't quote me on this but they may just be taking the absolute value for simplicity, since current can be taken as positive in one direction or negative to point in the other direction.
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