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Homework Help: Magnetic field of wire

  1. Mar 10, 2010 #1
    1. The problem statement, all variables and given/known data

    A long straight wire lies along the z-axis and carries an 8A current in the +z direction. Find the magnetic field (magnitude and direction) produced at x = 0.4m, y = 0, z = .3m by a .7mm segment of wire centered at the origin.

    2. Relevant equations

    B = u(0)I / 2piR

    3. The attempt at a solution

    b = (4(pi)x10^-7) (8A) / (2pi (.7x10^-3) ==> 2.3 mT(tesla)

    I think that's right, but I'm not sure where the magnitude and direction with the vectors come in. I'm assuming you subtract vector 1 from origin vector to leave .4i + .3k. Then do you take the magnitude and multiply it by b?

    Thanks for any help.
  2. jcsd
  3. Mar 10, 2010 #2


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    Homework Helper

    You didn't use the right equation to find B. B = u(0)I / 2piR is for an infinitely long wire, but the question asks for the field produced by a finite wire segment.
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