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Homework Help: Capacitor charging solved for time.

  1. Jan 22, 2013 #1
    1. The problem statement, all variables and given/known data
    Solving the equation: V = V0*[1 - e^(-t/RC)]

    2. Relevant equations
    Need to solve this equation for time to calculate the time at which a charging capacitor achieves a certain voltage across it's plates.

    3. The attempt at a solution
    I solve it as: t = -RC*ln(V/V0) but this doesn't seem to work. Help!
  2. jcsd
  3. Jan 22, 2013 #2


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    it looks like you might have done a step like this: ln(1+x) = ln(x) But this is not true.

    Edit: Oh, welcome to physicsforums by the way!
  4. Jan 22, 2013 #3

    rude man

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    Show your work step by step & we'll show you where you went wrong.
  5. Jan 22, 2013 #4


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    Or rather, ln(1-x) = ln(x)
  6. Jan 23, 2013 #5
    Thanks guys. I think our lecturer intends for us to sort of 'have a guess' by inspection and using time constant ratios than actually solve this, so I can leave it for another day, phew!
    Thank you for the feedback nonetheless.
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