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Energy in RLC circuit

  1. Dec 14, 2011 #1
    1. The problem statement, all variables and given/known data

    Please check picture

    http://i.imgur.com/YMQBR.png

    YMQBR.png

    2. Relevant equations



    3. The attempt at a solution

    Shouldn't all the energy be 0 at beginning?
    Thanks!
     

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  2. jcsd
  3. Dec 14, 2011 #2
    It tells you that this circuit is at resonance. Do you know what this means about the values of Xl, Xc and R.
     
  4. Dec 14, 2011 #3
    Xl = Xc

    R = R....
     
  5. Dec 14, 2011 #4
    The question doesn't make much sense!
    It is at resonance and that means:
    1) Xl = Xc
    2) Supply voltage and current are in phase
    3) Supply voltage is the voltage across R
    4) The power is dissipated in R
    This means that you can calculate the value of R. You are given the resonant frequency so you can calculate Xc and therefore Xl.
    I don't understand what they are asking !!!!
     
  6. Dec 14, 2011 #5

    ehild

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    Gold Member

    The problem asks about the energy stored in the inductor and in the capacitor, when the current is zero, so the voltage across the reactive elements is of maximum magnitude. You need the formula for the energy stored in an inductor and in a capacitor.
    t=0 does not mean that the source was switched on at that instant. The generator voltage has been the same before we started to measure time.

    ehild
     
  7. Dec 14, 2011 #6
    thank you!
     
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