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Magnetic Field of a bent infinite wire

  1. Mar 5, 2013 #1
    1. The problem statement, all variables and given/known data

    A long hairpin is formed by bending an infinitely long wire, as shown. If a current of 1.20 A is set up in the wire, what is the magnitude of the magnetic field at the point a? Assume R = 3.20 cm.

    http://lon-capa.mines.edu/res/csm/csmphyslib/type62_biotsavart_ampere/HairpinCurve.gif [Broken]
    2. Relevant equations

    dB=μ0*I*dlx[itex]\overline{r}[/itex]
    r^3
    3. The attempt at a solution

    I tried using the equation for two separate infinite lines and a full circle divided in half, and was unsuccessful. The same result occurred when i attempted to use the equation of a full line and a half circle. I came to the conclusion that i don't really know what Im doing when it comes to magnetism. any help would be greatly appreciated.
    1. The problem statement, all variables and given/known data



    2. Relevant equations



    3. The attempt at a solution
     
    Last edited by a moderator: May 6, 2017
  2. jcsd
  3. Mar 5, 2013 #2

    rude man

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    Can't access the link.
     
  4. Mar 5, 2013 #3
    Set it as an attachment. Thanks for the heads up
     

    Attached Files:

  5. Mar 5, 2013 #4
    Fixed my own problem.

    To anyone who might care, to solve this problem you can treat it as the sum of Biot-Savart Equations for an infinite line and a half circle, using R as your distance in both equations. I had attempted this once but didn't catch a sign error. Thanks anyway though.
     
  6. Mar 5, 2013 #5

    rude man

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    Set up x-y system with origin at point a. Then use Biot-Savart separately
    1) for the semicircle; easy integration since r is constant = R
    2) top straight stretch, and
    3) bottom straight stretch.

    For 2) and 3) you will be integrating dl from 0 to infinity where dl is an element of wire.
     
  7. Mar 5, 2013 #6

    rude man

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    Good point!
     
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