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Transient RC circuits.

  1. Dec 29, 2013 #1
    1. The problem statement, all variables and given/known data
    Determine the current flowing when the capacitor has been discharging for 5μs
    Capacitance=400 pico farads which is charged to 10v through a 50kΩ resistor.

    2. Relevant equations
    Vc = ve-t/CR

    3. The attempt at a solution So Vc =Ve -t/CR
    -t/CR = -5*10^-6/400*10^-12*50*10^3
    Which equals -0.25 so...
    Vc= 10*e-0.25
    Vc = 10*0.7788
    Vc = 7.788 volts after 5 micro seconds

    To find the current flowing after 5 micro seconds
    i = Vr/R since Vr=Vc Vc/R = 7.788/50000 = 0.156mA.
    Am i in the right ball park with this? Any guidance will be greatly appreciated.
  2. jcsd
  3. Dec 29, 2013 #2


    User Avatar

    Staff: Mentor

    Yup, looks fine.

    You could also have written the expression for the current ##I(t) = I_o e^{-\frac{t}{\tau}}## using the initial current Io from the initial conditions.
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