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Quick question about magnetic fields

  1. Mar 30, 2008 #1
    1. The problem statement, all variables and given/known data
    The force on a wire .80 m long that is perpendicular to the Earth's magnetic field is .12 N. What current flows throught the wire? (Earth's magnetic field is 1.0x10^-4 T at the poles and 5.0x10^-5 T at the equator)

    2. Relevant equations
    Fm is magnetic force in N, B is magnetic field strength in telsa (T), and l is length in meters.

    3. The attempt at a solution
    I'm just not sure what I'm supposed to use for B. Do I use the strength at the poles? at the equator? Some combination of the two?

  2. jcsd
  3. Mar 30, 2008 #2


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    Homework Helper

    This certainly is a mysterious problem statement: doesn't it say anything about where on Earth the wire is? Maybe you're supposed to find the range of possible values for the current within the range of values for the local magnetic field strength. Since we're told that the wire is perpendicular to the local field, the "magnetic dip angle" (angle the field makes to the local horizontal) doesn't matter. It seems like there's something left out of the problem...
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