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Homework Help: Solenoid equation help

  1. Nov 30, 2006 #1
    1. The problem statement, all variables and given/known data
    A long solenoid has 100 turns/cm and carries current i. An electron moves within the solenoid in a circle of radius 2.30 cm perpendicular to the solenoid axis. The speed of the electron is 0.04640c (c= speed of light). Find the current i in the solenoid

    B = permeability constant * i * 100turns/cm for the solenoid without the electron.

    I guess I need the speed of the electron somewhere.

    F = ma
    qvB = m (v^2)/r
    So we can get B of the circular loop.

    What do I do next? I don't suppose we just equate these two B's.
  2. jcsd
  3. Dec 1, 2006 #2


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    Science Advisor
    Homework Helper

    There's an idea. The only thing around producing a field to bend the path of that electron is the solenoid.
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