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Omggg Determining voltage between point a and b given R = 40 ohms

  1. Mar 8, 2013 #1
    Omggg :( Determining voltage between point a and b given R = 40 ohms

    PHYSICSHELP_zpse6fd0131.png

    This is what I did for part A:


    1) ΔVrms = Vmax(1/√2)
    ΔVrms = (145)(0.707)
    ΔVrms= 102.53

    2) Ztotal = √[R² + (XL - XC)²]

    XL = 2πfL
    XL = 2π(40)(185 x 10^-3)
    XL = 46.49

    XC = 1/2πfC
    XC = 1/[2π(40)(65 x 10^-6)
    XC = 1/0.016336382
    XC = 61.21

    Ztotal = √[40² + (46.49 - 61.2)²]
    Ztotal = √(1600 + 216.67)
    Ztotal= √(1816.67)
    Ztotal = 42.62

    3) ΔVrms = (Irms)(Zab)
    ΔVrms = (ΔVrms/Ztotal)(Zab)
    ΔVrms = (102.53/42.62)(40)
    ΔVrms = (2.405)(40)
    ΔVrms = 96.2 V

    :eek:
     
    Last edited: Mar 8, 2013
  2. jcsd
  3. Mar 8, 2013 #2

    gneill

    User Avatar

    Staff: Mentor

    For your Ztotal, why do you subtract the reactance component from the real (resistance) component when you summed them in quadrature (square root of sum of squares)?
     
  4. Mar 8, 2013 #3
    Oh oops, that's supposed to be a plus...

    But I still get the wrong answer :(

    I think I may have a mental breakdown...
     
  5. Mar 8, 2013 #4

    gneill

    User Avatar

    Staff: Mentor

    What value did you calculate?
     
  6. Mar 8, 2013 #5
    The answer is 96.2 :D
    Thanks for catching that!!!
    I think I've been studying for too long
     
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