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Moving charges and magnetism

  1. Jul 10, 2017 #1
    1. The problem statement, all variables and given/known data

    current in wire is in east to west direction.direction of magneetic field below the line
    2. Relevant equations
    right hand thumb rule
    3. The attempt at a solution
    i used the right hand thumb rule to find the direction of magnetic field but the magnetic field comes out in in the upwards direction(out of plane) but the answer is in the south direction
    my answer -upwards
    real answer-south

  2. jcsd
  3. Jul 10, 2017 #2


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    East to West defines a line, what plane do you speak about?
  4. Jul 10, 2017 #3


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    Gold Member

    Plane of the paper?
    I think your answer is right.
  5. Jul 10, 2017 #4


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    The paper can be horizontal, vertical, or can stand in any direction.

    East, West, North, South are defined in a horizontal plane.
    The magnetic field lines are circles around the wire, with the wire as axis. Take a pencil as wire and do the right thumb rule in reality. In what direction do your fingers point under the wire?
    This is a very bad drawing, I was not able to make a better one. The wire and the cardinal directions are in the horizontal plane.
  6. Jul 10, 2017 #5
    the plane of paper since north south east west are in plane of paper.
  7. Jul 10, 2017 #6
    this is the answer but my fingers are coming out of the plane of paper
    like this
    and this the actual question
    I could get the numerical answer but not the the direction
  8. Jul 10, 2017 #7


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    Your fingers come out of the paper beside the wire or above it. Just under the wire the fingers stand in the North-West direction, and having short fingers, the tips would point to the South. The green vector represents the direction of the magnetic field under the wire.

    This is a side view:

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