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Please help me with magnetic fields - how can i find its direction?

  1. Apr 27, 2005 #1
    Please help me with magnetic fields - how can i find its direction??

    The drawing shows two wires that carry the same current of I=85.0 A and are oriented perpendicular to the plane of the paper. The current in one wire is directed out of the paper, while the current in the other is directed into the paper. Find the magnitude and direction of the net magnetic field at point P.

    according to the answer,
    "The direction of B1 is 30.0° below the horizontal to the right. The direction of B2 is 30.0° below the horizontal to the left."

    but why??? if you use the RHR#2 (thumb into page for the one on the right, fingers curl in direction of magnetic field), isnt the magnetic field circular all around it? why is it in one direction?
     
  2. jcsd
  3. Apr 27, 2005 #2
    whoops heres the pic
     

    Attached Files:

  4. Apr 27, 2005 #3

    OlderDan

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    The answer given is talking about the fields AT POINT P and nowhere else. You have the RHR OK, but remember it applies to each individual point surrounding the wire.
     
  5. Apr 27, 2005 #4
    thanks
    but that doesnt add up..
    why is it just the field 30 degrees below the horizontal considered?
     
  6. Apr 27, 2005 #5
    hoops nm i think iget it
     
  7. Apr 27, 2005 #6
    thanks =)
    one more quick question
    how can u calculate that angle? (30degrees)
     
  8. Apr 27, 2005 #7

    OlderDan

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    It is an equilateral triangle. The slanted sides make an angle of 60 degrees with the horizontal. B is perpendicular to the line from each wire to P.
     
    Last edited: Apr 27, 2005
  9. Apr 27, 2005 #8
    gotcha
    thanks
     
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