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Electromagnetic induction question

  1. Apr 24, 2007 #1
    How do I calculate the force (in newtons) acting on a conductor moving through a magnetic field? This is in relation to an electromagnetic brake by the way; I need to work out the deceleration of train as it moves through the braking zone.

  2. jcsd
  3. Apr 24, 2007 #2
    Force is [tex]\vec F=I\ell \vec u\times\vec B[/tex]
    Here [tex] \vec u[/tex] is a vector parallel to the current and pointing in the same direction.
    [tex]I[/tex] and [tex]\ell[/tex] are the current and the conductor length.
  4. Apr 24, 2007 #3
    Thanks! As an aside, how would you work it out if you use a permanent magnet rather than an electromagnet?
  5. Apr 24, 2007 #4
    The origin of B doesn't matter, it can be generated by an electromagnet as well as by a permanent magnet.
  6. Apr 24, 2007 #5
    so the equation remains the same? does that mean there has to be a current in the conductor rather than in the magnet?
  7. Apr 24, 2007 #6
    Yes. No current, no force.
    In a magnetic brake the current in induced by the varying magnetic flux.
    Only electromagnets need current to generate the magnetic field.
  8. Apr 24, 2007 #7
    Thanks for all that, I wish I'd had this discussion 2 months ago - would have made a project much easier.
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