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Homework Help: Please help me simplify this equation >_<

  1. Mar 17, 2005 #1
    [tex]B = uNI/2L * (L/2/(\sqrt{((L/2)^2)+R^2)} - (-L/2/(\sqrt{((-L/2))^2+R^2))}[/tex]

    I get.. [tex]B = uNI/2R[/tex] (for those wondering, this is the equation to find the magnetic field when a Hall probe is placed in the center of a solenoid)

    they ask me to figure out the % diffeerence between the field at the center of the solenoid compared to a solenoid that infinitely long (where B = uNI)..

    I get L = 28cm, R = 2.69cm, I = 1.25A

    i get 520% when using my simplified formula >_<
    is this right???

    and i dont even use the current!
    Last edited: Mar 17, 2005
  2. jcsd
  3. Mar 17, 2005 #2


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    Science Advisor

    It's hard to tell- you are clearly missing at least one parenthesis. Is the initial
    (uNI/2L) multiplied by BOTH fractions (in which case they clearly add) or is it multiplying only the first fraction (which is what you have written- and is much harder).
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