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Homework Help: Magnetic Field and Force (in a solenoid)

  1. Feb 26, 2012 #1
    1. The problem statement, all variables and given/known data

    A 200-turn solenoid is 20.0 cm long and carries a current of 3.25 A. Find the magnetic field. Find the force exerted on a 15.0 µC charged particle moving at 1050 m/s through the interior of the solenoid, at an angle of 11.5° relative to the solenoid’s axis.

    2. Relevant equations

    torque=IABn (n=turns)

    3. The attempt at a solution


    If I want to use torque=IABn to find B I need torque and I do not know how to find it with the length only. The second part I understand once I find the Magnetic Field, but I dont get how to find it with the info given.

    the answer key says: B=4.08 x 10-3 T and F=1.28 x 10-5 N
  2. jcsd
  3. Feb 26, 2012 #2

    I like Serena

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    Homework Helper


    I think you need an extra formula.
    The magnetic field inside a long solenoid is given by:
    $$B=\mu_0 {n I \over \mathcal{l}}$$
    as you can see on wiki: http://en.wikipedia.org/wiki/Solenoid
  4. Feb 26, 2012 #3
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