Resonance series and parallel

Discussion in 'Homework Help' started by xx123321, May 4, 2011.

  1. xx123321

    Thread Starter New Member

    Apr 27, 2011
    15
    0
    hi,every guys,i am currently having difficulty with a RLC resonant circuit.

    First of all,what's the relationship between VR and VC?
    In addition, i am confused by some terms in resonant circuit.
    what're the meaning of following terms:
    1-fs
    2-fp
    3-Qs
    4-Ql
    5-Qp
     
  2. beenthere

    Retired Moderator

    Apr 20, 2004
    15,815
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    You might get better help if you post the circuits. You do know that LC resonance occurs when Xc = Xl?
     
  3. xx123321

    Thread Starter New Member

    Apr 27, 2011
    15
    0
    UPDATE the circuit as follow,
    [​IMG]
    I know that resonance occurs when XL=XC.
     
  4. beenthere

    Retired Moderator

    Apr 20, 2004
    15,815
    282
    That's a series circuit. No frequency is given from the source, so you need to find the F that makes Xc = Xl. R is there for a reason.
     
  5. xx123321

    Thread Starter New Member

    Apr 27, 2011
    15
    0
    Assume that's a resonant circuit, so Xc=Xl=30 ohm ,it that right?
    Then how about my questions posted at #1 ?
     
  6. jegues

    Well-Known Member

    Sep 13, 2010
    735
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    He had asked you about the frequency.

    Starting with Xc=Xl, can you obtain f_{o}?
     
  7. xx123321

    Thread Starter New Member

    Apr 27, 2011
    15
    0
    frequency is 5k Hz
     
  8. jegues

    Well-Known Member

    Sep 13, 2010
    735
    43
    Can you show us how you obtained a value of 5KHz?
     
  9. xx123321

    Thread Starter New Member

    Apr 27, 2011
    15
    0
    I am sorry about that i haven't express the question clearly,the question haven't gave any frequency,the source is 50mV only.

    Here is the original question:
    The question is "Refer to the resonant circuit in figure 1 (posted at #3) ,determine:
    (a)the value of Xc --->is the answer 30ohm?
    (b)total impedance
    (c)current
    (d)Vr,Vl and Vc at resonance
    (e)The relationship between Vr and Vc

    I have figured out (a),(b),(c),(d) but i am stuck at (e)
     
  10. t_n_k

    AAC Fanatic!

    Mar 6, 2009
    5,448
    782
    The OP's original question asked what was the relationship between VR & VC in the series circuit - at resonance.

    There's no need to find the resonant frequency.

    At resonance VR & VC are orthogonal and for the given circuit have a magnitude ratio |VR/VC|=1/3. VR will be 50mV and in phase with the source E.

    One could guess the context of the other matters - presumably they relate to resonant frequencies and Q factor values in series and parallel resonant circuits. I don't think anyone is really interested in explaining these terms when they are well defined in any number of text books or web pages.

    Such as ....

    http://www.allaboutcircuits.com/vol_2/chpt_6/6.html
     
  11. xx123321

    Thread Starter New Member

    Apr 27, 2011
    15
    0
    Thanks all guys,now i know how to sort it out.
     
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