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Homework Help: Frequency of Generator + V of Capacitor

  1. Mar 19, 2007 #1
    1. A 8.6 Hz generator is connected to a capacitor. If the current in the generator has its maximum value at t=0 s, what is the earliest possible time that the voltage magnitude across the capacitor is at a maximum?

    2. I'm actually not sure which equations are relevant for this problem!

    3. I'm afraid I don't understand the concepts behind this problem. I read in my book about oscillations in an LC circuit with no generator, but then I don't understand how this can be applied when there *is* a generator with its own frequency. Any help would be appreciated!
  2. jcsd
  3. Mar 19, 2007 #2


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    Gold Member

    It depends on the waveform of the generator. If we assume sinusoidal then the voltage from the generator is V*cos(2*pi*8.6*t) which has its maximum V when t=0 as required. Find the formula that tells you how a capacitor charges and you're halfway there.
  4. Mar 19, 2007 #3


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    Staff: Mentor

    Except the problem statement says that the current is max at t=0, not the voltage. kmj9k, what is the relationship between voltage and current in a capacitor? Assume a sinusoidal waveform along the lines of what Mentz suggested....will the current lead or lag the voltage in a capacitor?
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