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Homework Help: Explanation of quality factors for a circuit

  1. May 30, 2012 #1
    1. The problem statement, all variables and given/known data

    What does it mean physically if Q < 1 for a particular circuit? What would happen, for
    instance, if a switch were suddenly closed which completed the circuit by a wire rather
    than the ac supply?

    2. Relevant equations

    I've already derived the equation for Q (the quality factor)
    Q = 1/R *(L/C)^.5

    3. The attempt at a solution

    When Q is less than 1 this means that energy dissipated during a period is greater than the energy store. I also know that the bandwidth is wide when Q is small. I'm not sure how else to answer the question.
  2. jcsd
  3. May 31, 2012 #2

    rude man

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    Homework Helper
    Gold Member

    You have already answered the question correctly. More exactly:
    Q = 2π*(max energy stored within 1 cycle)/(energy dissipated per cycle).

    In a series R-L-C circuit at resonance, total energy stored is a constant so you don't need to specify "peak". In this case, an equally valid definition of Q is ω0/Δω

    where ω is radian frequency and Δω is the half-power bandwidth.
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