Electromagnetic induction question

  • #1

Main Question or Discussion Point

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.

Thanks.
 

Answers and Replies

  • #2
388
3
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.
 
  • #3
Thanks! As an aside, how would you work it out if you use a permanent magnet rather than an electromagnet?
 
  • #4
388
3
The origin of B doesn't matter, it can be generated by an electromagnet as well as by a permanent magnet.
 
  • #5
so the equation remains the same? does that mean there has to be a current in the conductor rather than in the magnet?
 
  • #6
388
3
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.
 
  • #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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