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Homework Help: Magnetic fields and charged particles

  1. Mar 7, 2012 #1
    It has been stated that a charged particle in the vicinity of a magnetic field experiences a force given by F = qV x B, which states that there is no force when its velocity is zero. It also shows that only the particles direction can be changed, not its kinetic energy.

    My question is this: what if you take the frame of reference that the particle has zero velocity and the magnetic field is moving (or changing)? Or simply, you have a stationary charge and pass a magnetic field by it?

    In this context, is the kinetic energy of the particle then changed?

    If so, is this at all related to, or the base idea of induction?
  2. jcsd
  3. Mar 7, 2012 #2


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  4. Mar 7, 2012 #3
    When you use F=qv×B this equation, v must be in reference to a non-changing B. If you want to use the reference frame in which the particle is the center of coordinates (ie. v=0), then you must use the induction laws, specifically:

    E.dl = -(d/dt)∫∫B.dS, and F=qE

    PS. It's so much easier to just use F=qv×B.
    Last edited: Mar 7, 2012
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