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Magnetic field of a wire with current running through it

  1. May 24, 2009 #1
    on an x,y,z axis i have a wire with infinite length placed on the z axis with a current of 2A running through it downwards, in addition i have a magnetic field of 2*10-7T in the Y+ direction, what is the magnetic firld at
    A(1,0,0)
    B(0,1,0)
    C(-1,0,0)

    i know that my field at each point must be the sum of the fields at the points, so it will be 2*10-7T*Y + the field of the wire,


    what equation cani use to find the field of an endless wire??
     
  2. jcsd
  3. May 24, 2009 #2

    tiny-tim

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    You tell us! :wink:

    you'll have to integrate over ds from -∞ to +∞ :smile:
     
  4. May 24, 2009 #3
    i thought that might be it, using Biot-Savart Law?

    dB=μ0I/(4∏)*dlxr/r3
    but since the wire is 90 degrees to r
    dB=μ0I/(4∏)*dl/r2

    B=∫μ0I/(4∏)*dl/r2
    B=μ0I/(4∏r2)*∫dl

    but that will give me infinity???
     
    Last edited: May 24, 2009
  5. May 24, 2009 #4

    tiny-tim

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    ?? :confused:

    you haven't included the variation in distance (use Pythagoras)

    (oooh … and have a small pi: π :wink:)

    EDIT: hello Redbelly! o:)
     
  6. May 24, 2009 #5

    Redbelly98

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    The wire is not at 90 degrees to r everywhere:

    http://electron9.phys.utk.edu/phys136d/modules/m7/images/dl.gif [Broken]

    That being said ... doesn't your textbook discuss the magnetic field of a long straight wire???
     
    Last edited by a moderator: May 4, 2017
  7. May 24, 2009 #6
    so would i say r=sqrt(1+L^2) ??

    dB=μ0I/(4∏)*dL/(1+L^2)
     
  8. May 25, 2009 #7

    tiny-tim

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    yes, except these are vectors, so you need a cosine in there, don't you? :wink:
     
  9. May 25, 2009 #8

    Redbelly98

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    Or perhaps a sine?

    p.s. Hello tiny-tim :smile:
     
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