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Multisim rms current and voltage RLC Circuit

  1. May 22, 2013 #1
    Trying to find rms current at resonance and rms voltage across each elements (resistor, inductor and capacitor)

    I got the answers but i want it do in multisim !!

    i got :

    R = 500 ohm
    L = 0.40mH
    C = 100pF

    The answer is

    rms current: 0.002A
    rms voltage:
    Vr = 1V
    Vc = 126.52 V
    Vl = 126.52 V

    The resonant freq. is 25.16 Khz at 1v RMS ac source.

    [Broken]
    this is my attempt !!!
    1. The problem statement, all variables and given/known data



    2. Relevant equations



    3. The attempt at a solution
     
    Last edited by a moderator: May 6, 2017
  2. jcsd
  3. May 22, 2013 #2

    gneill

    User Avatar

    Staff: Mentor

    How did you arrive at the resonant frequency? It looks a bit small to me, given the stated component values.
     
  4. May 22, 2013 #3

    sorry this is the answers

    A) resonant frequency
    ans: f = 1/2*pi*sqrt(LC)
    = 1/(2*pi*sqrt(0.0004 * 100 * 10^-12)
    = 795.77 Khz

    b) the inductive and capacitive reactance at resonance
    ans: XL = 2*pi*f*L
    = 2*pi* 795.775*10^3*0.0004
    = 2000 ohm

    Xc = 1/(2*pi*f*C)
    = 1/(2*pi* 795.775*10^3 * 100 * 10^-12)
    = 1999.9998 ohm

    C) the impedance at resonance

    ans : impedence of resonance is resistance of circuit : z = R = 500 ohm

    D) the rms current at resonance
    ans: I = V/R = 1/500 = 0.002A

    E) the rms voltage across each element at resonance
    Ans: Vr = IR
    = 0.002 * 500
    = 1V

    VL = IXL
    = 0.002 * 2000
    = 4V

    Vc = IXc
    = 0.002 * 1999.99
    = 3.99998 V
     
  5. May 22, 2013 #4

    gneill

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    Staff: Mentor

    Yes, that looks better.
     
  6. May 22, 2013 #5
    but still i cant prove into multisim !!!
     
  7. May 22, 2013 #6

    gneill

    User Avatar

    Staff: Mentor

    I don't have Multisim, so I can't help with the details of using it. Sorry.

    But looking at the image you've provided, I would say that there sure are a lot of multimeters inserted, presumably to measure current. Surely one would suffice for a series circuit? Also, it appears that the inductor's top end is open circuited and it is being bypassed by a multipmeter (to measure voltage?). I'd suggest removing all but one multimeter to measure the series current, and make sure that the circuit is unbroken and operational before adding multimeters in parallel with the components to measure their voltages.
     
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