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Homework Help: Magnetic flux in spool.

  1. Mar 24, 2014 #1
    1. The problem statement, all variables and given/known data

    The attached picture shows a spool coil on a iron core with an air gap measuring 2.5mm. The spool is coiled by 0.5mm2 with rho cu = 0.0175 Ωmm2 /m. The average winding diameter for the spool is 3.18cm.

    Compute the magnetic flux in the spool.

    2. Relevant equations

    3. The attempt at a solution

    Using the equation: phi = I * N / Rm, I still miss I, and I have no idea how to compute it. Rm is the reluctance which I can get from a B-H characteristic - if that applies to this problem.

    My first questions are these I guess: Is this the correct formula? If yes, how to I compute I?

    Any feedback and help is as always greatly appreciated. Thanks.

    Attached Files:

  2. jcsd
  3. Mar 24, 2014 #2

    rude man

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    Your formula is fine but you need to use the correct reluctance.
    You also need either the voltage or the current in the spool.

    Hint: the reluctance of the air gap is >> reluctance of the rest of the core. Forget B-H of the core!
  4. Mar 24, 2014 #3
    If I need the voltage or current, it would apprear it's missing from the problem - and I do apologize for that. But since you say I can use the voltage, how should I go about it if we set the voltage to 24V?
  5. Mar 24, 2014 #4

    rude man

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    Per your equation, you need the current, right?
  6. Mar 24, 2014 #5
    Yes, but the voltage is given at a later problem, so I figured why not just test it now as I'm not sure what to do. If I have the current, I would just need to plot it + find the correct reluctance to proceed.

    I don't know though, it was just an idea.
  7. Mar 24, 2014 #6

    rude man

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    get the current, by hook or by crook!
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