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Homework Help: Transmission Line, voltage drop

  1. Nov 24, 2009 #1
    1. The problem statement, all variables and given/known data

    Prove that for a line having resistance R, and reactance X, and supplying load of P+jQ has an approximate voltage drop of:

    Vr = [RP+XQ]/Vs

    2. Relevant equations

    none given.

    3. The attempt at a solution

    I made a diagram, with R, X, and P+jQ in series. Vr is the potential drop across the load, and Vs is the supplying voltage. I've tried every method, but it doesn't turn out to be the given answer. I've covered two pages worth of pointless calculations, and it just doesn't seem to work out.

    help me as soon as possible.

    thanks :)

  2. jcsd
  3. Nov 24, 2009 #2


    User Avatar

    Staff: Mentor

    Welcome to the PF. I think there must be a typo in your "solution" equation:

    Vr = [RP+XQ]/Vs

    If I interpret your variables correctly, you are saying that units of Volts^2 = units of Ohms^2

    Doesn't look right...
  4. Nov 25, 2009 #3
    i'll look over it, but thats what it says on the question paper.

    thank you for pointing it out, i should've noticed this ! :p

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