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Homework Help: Magnetism problem

  1. Feb 20, 2006 #1
    An electron of mass 9.11 x 10-31 (9.11e-31) kg travels in a circular orbit within a large evacuated chamber. The orbit has a 2.0 mm radius and is perpendicular to a B-field of 0.030 T. What's the electron's speed?

    For this problem, the only equation i can think to apply is F=qvB.

    I know B, i know q, i need to solve for V, but how do i get F?

    F =ma, but that still leaves me stuck because i dont know the acceleration of the electron...

    I understand this problem and know what to do, i'm just missing something somewhere because i don't seem to have enough to solve the problem, although i know its in there. I'm just not seeing it, and need a slight prod in the right direction.
  2. jcsd
  3. Feb 20, 2006 #2
    I am not sure but,
    F=qvb and
    so qvb=ma?
    I am confuse as you are.
  4. Feb 20, 2006 #3
    Remember that the electron travles in a circular orbit with a constant velocity, so you also have this equation

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