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Homework Help: Magnetism question

  1. Apr 29, 2007 #1
    1. The problem statement, all variables and given/known data

    A compas needle points 20 degrees East of North outdoors. However, when it is placed 8cm to the east of a vertical wire inside a building, it points 55 degrees east of north. what is the magnitude and the direction of the current in the wire? the earth's field is 5.0E-5 and is horizontal

    2. Relevant equations

    Sin=O/H Cos=A/H

    B=UI/ 2(pi)R

    3. The attempt at a solution

    i solved for the horizontal and vertical components of the earths magnetic field and found the components for the x and y to be 4.56E-5 and 2.04E-5 respectively.

    i am stuck on how to find the components for the magnetic field of the wire.

    any help will be greatly appreciated
     
  2. jcsd
  3. Apr 29, 2007 #2
    What do the magnetic field lines around a wire look like?
     
  4. Apr 29, 2007 #3
    there is no diagram, that is all the information given about the problem. i copied the problem word for word out of the book.
     
  5. Apr 29, 2007 #4
    You didn't cover magnetic field lines in class? The book doesn't cover them in the section preceding the problem?
     
  6. Apr 30, 2007 #5
    it does, but it doesnt cover this type of question.
     
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