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Homework Help: Motional EMF in Transportation

  1. Oct 29, 2012 #1
    1. The problem statement, all variables and given/known data
    Airplanes and trains move through the earth's magnetic field at rather high speeds, so it is reasonable to wonder whether this field can have a substantial effect on them. We shall use a typical value of 0.50 G for the earth's field.

    A) The French TGV train and Japanese "bullet train" reach speeds of up to 180mph with wheels moving on tracks about 1.5m apart. At top speed moving perpendicular to the earth’s magnetic field, what potential difference is induced across the tracks as the wheels roll?

    B) The Boeing 747-400 series of aircraft has a wingspan of 64.4m and a cruising speed of 565mph . If there is no wind blowing (so that this is also their speed relative to the ground),what is the maximum potential difference that could be induced between the opposite tips of the wings?

    (Both answers expected in mV)

    2. Relevant equations

    EMF = vBL (I think?)
    180mph = 80.4672 m/s
    0.5G = 0.00005 T

    3. The attempt at a solution

    I've tried using vBL, but to no avail. I have v and B, as they are given. The problem seems to be finding an L that works. At first I used 1.5m, the distance between the rails, but I realized that's wrong because it's not perpendicular to B. I've tried the distance the train travels in 1 second, 80.4672 m, but that does not work either.

    Is there some other equation that I'm not seeing?
  2. jcsd
  3. Oct 29, 2012 #2
    1 G = 10-5 T
    0.5 G = 0.000005 T
    You need an extra 0
    It should work with 1.5 m. What do you get?
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