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Capacitor Equations

  1. Jun 17, 2017 #1
    1. The problem statement, all variables and given/known data
    Hi, i've run into two different equations for the voltage of a typical RC circuit, one resistor, and one capacitor.
    Please explain the different between the two. One has a 1 - the natural log and the other one doesnt.

    2. Relevant equations
    1. V(t) = Vo*e^(-t/RC)

    2. Vc = Vs(1-e^-t/RC)

    3. The attempt at a solution
     
  2. jcsd
  3. Jun 17, 2017 #2

    kuruman

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    One of the equations is for a charging capacitor and the other for a discharging capacitor. To figure out which is which, evaluate each expression at t = 0 and at t → ∞ .
     
  4. Jun 17, 2017 #3
    thanks!
     
  5. Jun 18, 2017 #4

    haruspex

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    It is not a log; it is a negative exponential.
    Do you understand what these two curves look like?
     
  6. Jun 18, 2017 #5
    Typo, yes it is the natural exponent. I dont know why but i was thinking exponent and typed log. They are inverse of each other.
     
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