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Homework Help: Force on Current Carrying Wire

  1. Feb 17, 2005 #1
    For the life of me I can't seem to get the right answer for this problem!
    A horizontal power line carries a current of 5000A from south to north. Earth's magnetic field (60.0 microT) is directed toward the north and inclined downward at 70.0 degrees to the horizontal. Find the (a) magnitude and (b) direction of the magnetic force on the 100m of the line due to Earth's field.
    So here's what I've been thinking so far: first off you're using F=iLxB here where your L vector's going to point in the j direction. By this point I've sufficiently confused myself to the point where I'm not sure if you need a sin(70) for the j direction or not... hmmmm. I'm pretty confident that I can cross the vectors alright which sort of implies I've messed up somewhere else, I'm thinking maybe my B vector...
    Any advice would be appreciated. :smile:
  2. jcsd
  3. Feb 17, 2005 #2


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    I'm not sure what L and i are, but yes, sin(70) will be useful.
  4. Feb 18, 2005 #3
    Ah ok, figured out what I was doing wrong (it's supposed to be an angle of 20 degrees instead of 70... *bangs head*). So all's well that ends well.
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