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Homework Help: Magnetic field from four parallel wires

  1. Oct 19, 2012 #1
    1. The problem statement, all variables and given/known data

    I am looking at four parallel wires of finite length L, whose currents run in the directions shown in the attached figure. There is no gradient along the wire-axis, so from Maxwell's equation
    \frac{dB_x}{dx} = -\frac{dB_y}{dy} \equiv \tilde B.
    In order to find an expression for the gradient [itex]\tilde B[/itex] given some current I, I need to use Biot-Savarts law. I think I need to make a binomial expansion for small displacements from the center, but I am not quite sure how to do this with the Biot-Savart law. I would really appreciate a hint.


    Attached Files:

  2. jcsd
  3. Oct 20, 2012 #2
    Or you could simply superimpose 4 fields from the individual wires. I would imagine you've already solved the field for a single wire, so B=B1+B2+B3+B4. Remember, the wires aren't all in the same direction, so you have to add some and subtract others.

    Once you've resolved all your issues https://www.physicsforums.com/showthread.php?t=645327, you should be able to write everything in terms of the x and y components of the 4 wires.
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