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Calculating the direction of Earth's magnetic field

  1. Mar 17, 2013 #1
    Please help! Calculating the direction of Earth's magnetic field

    1. The problem statement, all variables and given/known data

    Calculate the direction of Earth's magnetic field.

    2. Relevant equations



    3. The attempt at a solution

    3 components of the magnetic field:

    Geographic South to North: 0.01670 mT
    Geographic West to East: 0.002147 mT
    Up to down (up is the sky, down is the ground): 0.03722 mT

    Calculating angle East of North:

    tanθ=0.002147/0.01670
    θ=7.33° East of North

    Angle below horizontal:

    tanθ=0.03722/√(0.016702+0.0021472)
    θ=65.66° below horizontal

    Is my attempt correct?
     
    Last edited: Mar 17, 2013
  2. jcsd
  3. Mar 17, 2013 #2
    If I did the first question correctly, I need help with this question:

    Compare the direction of the projection of this magnetic field vector on the horizontal
    plane (the angle to the east (or west) of geographic north) with the direction of the
    compass.

    I honestly don't understand what they're asking here. Are they saying to compare 7.33° with the direction of the compass? How do I find the direction of the compass?
     
  4. Mar 17, 2013 #3
    Also, one last question:

    The magnetic field in anywhere between two helmholtz coils is uniform, right?
     
  5. Mar 17, 2013 #4
    Anybody? This is due tomorrow. :|
     
  6. Mar 17, 2013 #5

    haruspex

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    Your answer looks fine. I am similarly bemused by the second question. Since it says "the compass", I would expect it to be in the context of some actual compass described or supplied elsewhere.
     
  7. Mar 17, 2013 #6
    Maybe they're asking to check the percent error compared to the real value?
     
  8. Mar 17, 2013 #7

    haruspex

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    It's not a percent error.
    By 'real' value, do you mean true north, or the known declination for where you are?
     
  9. Mar 17, 2013 #8
  10. Mar 17, 2013 #9
    I have no idea.

    Don't worry about it. I'm just going to hand in what I have. No point stressing over it since no other students seem to know the answers either.
     
  11. Mar 17, 2013 #10

    haruspex

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    When you fill in the data table for e.g. the NS field, how are you determining that it's NS? Do you use the compass for that? If so, are you taking it from the magnetic N according to the compass, or are you correcting for declination?
     
  12. Mar 17, 2013 #11
    Yes.

    I am taking it from the magnetic N according to the compass.
     
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