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Homework Help: Electric energy in a capacitor

  1. Mar 29, 2009 #1
    1. The problem statement, all variables and given/known data

    part 1. Consider a simple RC circuit consisting of a resistor and a capacitor connected in series to a battery. The resistor has a value of 8kOhms, and the capacitance is 3uF. The final (asymptotic) value of the charge in the capacitor is E*C. At what time is the charge in the capacitor one half of this final value?

    part 2. At what time is the electric energy in the capacitor one-half of its final value?

    2. Relevant equations

    Q(t) = EC(1-e^(t/(RC)))
    E = Voltage
    C = Capacitance
    t = time

    3. The attempt at a solution

    for part 1, i set (1-e^(t/(RC))) = .5*EC and got a time of .0218.
    for part 2, i don't know the equation to relate electric energy of a capacitor over time. i think that's all i need is just the equation.

    thanks in advance!
  2. jcsd
  3. Mar 29, 2009 #2


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