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Maglev estimate

  1. Mar 4, 2004 #1

    I am trying to get a rough estimate for the B-field (from a electromagnet) required to levitate a train.

    Assuming the train is of mass M, the force required to lift it and hold it at a distance D would have to equal M x g right?

    But how do i estimate the b-field an electromagnet would have to generate to make this happen?

    Thanks for any help!

  2. jcsd
  3. Mar 4, 2004 #2


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    Homework Helper

    It isn't the B-field directly, but the gradient of the B-field that motivates ferromagnetic material (that isn't magnetized, as I'm assuming the train of interest is not magnetized). Then, the calculation basically involves the magnetic energy density just abolve the train, just inside the top of the train, just below the train, and just inside the bottom of the train. If the magnetic energy decreases by an amount greater than the gravitational potential energy increases for an upward displacement, then the gradient is sufficient to levitate the train.

    I would suggest modelling the train by a long skinny rectangular prism, and approximate the B-field as cylindrically radially uniform (only an axial gradient).

    Magnetic energy density:

    uB = B2/(2μ0)

    Gravitational potential energy:

    UG = mgh
  4. Mar 12, 2004 #3
    sorry for a late reply, but thanks! massive help.
    Now just have to put in some guesstimate figures and come up with an estimate.


    peteBoy Rocket!
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