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Basic maths now doing my head in

  1. Jun 23, 2014 #1
    Hi guys,

    Firstly I apologise that I'm even asking this.... I have gone over it so many times now I don't know what to believe is the right answer, can someone please help me out and let me know where I'm going wrong PLEASE

    Ok so first is the inductive impedance

    Z= SQRT R^2 + (WL)^2

    R = 2.7*10^6 2.7MĪ©
    W= 2piF = 2pi*10 2pi*10Hz
    L= 300*10^-3 300mH

    R^2 = 7.29*10^12
    WL = 18.84955592 WL^2 = 355.3057584
    R^2+WL^2 = 7.29*10^12 + 355.3057584 =7.29*10^12

    How can that be right? I may of well just squared R to start with... so what am I doing wrong???


    Impedance in RLC circuits

    Z= SQRT R^2 +(Xl - Xc)2

    W = 2piF = 628318.5307

    F = 100*10^3 = 100000
    C = 300*10^-6 = 3*10^-4
    L = 300*10^-3 = 0.3
    R = 2.7*10^6 = 2700000
    Xl = WL = 188495.5592
    Xc = 1/WC = 5.30516477*10-3

    so R^2 +(Xl - XC)^2 = 7.325530574*10^12 and to me that just does not seem the right answer??

    Can you guys see where I would be going wrong? and if so how do I put it in to my calculator?
    Many thanks
  2. jcsd
  3. Jun 23, 2014 #2


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    Staff Emeritus
    Science Advisor
    Gold Member

    Why do you think you are doing something wrong? The reactance factors are frequency dependent. What you have learned is that at 10Hz (a very low frequency) the reactive elements have very little effect. Try higher frequencies.

    Side note. Do NOT copy every digit off of your calculator display. It would do you much good to find a explanation of significant digits. This bit of work will save you time and effort in the future.
  4. Jun 24, 2014 #3
    I just don't think it's right? and when I go to a online calculator I get different answers.

    My maths is not that great to say the least, so to be honest I don't know what is significant and what isn't (sorry)
  5. Jun 24, 2014 #4


    User Avatar

    Staff: Mentor

    Don't forget to take the square root, to end up with Z.
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