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Homework Help: Magnetic field problem

  1. Apr 5, 2005 #1
    a three phase transmission line consists of three conductors that are supported at points A,B, c to form an equilateral triangle. At one instant, conductors A and B both carry a current of 75A while conductor C carries a return current of 150 A. Find the force per meter on conductor C at that instant.

    heres what it looks like


    current at A and B is going in, current at C is coming out. Each point is 2 meters apart.

    This is the z = 0 plane
    im really stuck on this one.
  2. jcsd
  3. Apr 5, 2005 #2
    Where are you stuck, what have you tried?

    Spit out some equations you think might fit.
  4. Apr 5, 2005 #3
    the only think i can think of is to find the H field about A and B with rho being equal to the distance to C. than use the int(i*dl cross B). do that at A and B ? i dont see how the 150 amp current causes a force at C.
  5. Apr 5, 2005 #4
    The force on a charge due to magnetic field from each wire will be:

    [tex] F = i\int{B\times dl} [/tex]

    Now you'll want to find the force for wires A and B at point C. Does the current through C affect the magnetic field? How so?
  6. Apr 5, 2005 #5
    since the current at C is twice at the current at A and B than wouldnt that cancel out the magnetic field?
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