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Homework Help: Electricity and Magnetism question

  1. Mar 5, 2006 #1
    A solenoid 2.9 cm in diameter and 15 cm in length has 300 turns and carries a current of 5 A. Calculate the magnetic flux through the circular cross-sectional area of the solenoid.

    -->> I tried using the equation B = u(0)NI/L to calculate magnetic field, and then putting this in the formula flux = BNA, where N is number of turns, and A is area (pi*r squared). This didn't work, though.

    I'd appreciate some help!!! Thanks!
  2. jcsd
  3. Mar 6, 2006 #2
    The field is indeed given by

    and the total flux through the solenoid
    [tex]\phi=NAB[/tex] is also right.

    Maybe what they asked for is the flux through a single turn which would be your answer divided by N

    Also keep in mind that
    is valid only for a long solenoid. (When its length is large compared to its radius)

    I feel your solenoid is long enough. I don;t see why you're not arriving at the answer.
  4. Mar 6, 2006 #3
    yep, it was wanting it through one turn. thanks.
  5. Mar 7, 2006 #4


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    I think NBA is the total flux linked with the solenoid, not the flux through the cross-section. It is BA only.

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