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Homework Help: Plane immersed in the earth's vertically downward-pointing magnetic field

  1. Oct 24, 2011 #1
    1. The problem statement, all variables and given/known data

    This question and the next two refer to this situation:



    A passenger jet is flying over Alaska in level flight at a constant altitude h = 10 km and constant speed of v = 300 m/s, immersed in the earth's vertically downward-pointing magnetic field of B = 30 μT. The distance between the tips of the aircraft's metal wings is d = 50 m.

    Part A:
    Calculate the potential difference ε between the aircraft's wing tips due its motion through the earth's magnetic field.
    (a) ε = 0.0 volts
    (b) ε = 0.45 volts
    (c) ε = 0.90 volts

    Answer is B

    Part B
    Which wingtip has positive charge, as viewed by a passenger in the airplane who is facing in the direction that the airplane is traveling?
    (a) the right wingtip
    (b) the left wingtip
    (c) neither wingtip

    Answer is B

    2. Relevant equations

    emf = d flux / dt

    flux = int[B*dA]

    3. The attempt at a solution

    For part A, I tried formula above, I get answer C, because I thought I need to calculate difference for both wings? Part B I used F=BIL, however, I get the force is on right wing? What is the relationship between force ans its direction of the plane that traveling?

  2. jcsd
  3. Oct 24, 2011 #2


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    Homework Helper

    For part A, I used the generator formula V = L*v*B = 50*300*30x10^-6 = 0.45 Volts. Had I used only one wing length I would have gotten half that voltage.

    Part B is not a formula question. Use hand rules to figure out which way the electrons are pushed. Then you can tell which side is negative and which is positive.
  4. Oct 25, 2011 #3
    Everything makes sense now, thanks!
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