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Homework Help: Electromagnetics = Biot-Savart Law around square path

  1. Apr 15, 2010 #1
    1. The problem statement, all variables and given/known data
    Find the B-field at the center of the square loop located above the xy plane, with width (w), and current I rotating counter-clockwise.

    2. Relevant equations
    Here is the given equation:
    B = [(μo*I*aФ)/(4∏*ρ)](cosα2 – cosα1)

    The final answer is for the B-field about the loop is:
    B = [(4μo*I)/(∏*w*(√2))]az
    How do I obtain this answer? I am having trouble with the angles that I am supposed to use.
    3. The attempt at a solution
    I used (w/2) for the radial component, ρ. I used 45 degrees for α2, and 90 degrees for cosα1, and this is obviously wrong. Which angles do I use to get the correct angle?
    Last edited: Apr 15, 2010
  2. jcsd
  3. Apr 15, 2010 #2
    Solving this analytically for cosα2 - cosa1, I should receive 2/sqrt(2). How should I set up my angles to acheive this? Thank you for all help, I greatly appreciate it!
  4. Apr 15, 2010 #3


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    What kind of picture goes with the given equation? In other words, for what situation was it derived? How are ρ, α1 and α2 defined?
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