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Which length has to be taken to compute magnetic resistance?

  1. Aug 12, 2015 #1
    In general I read that:

    [itex]R_m =\frac{l}{\mu A}[/itex]

    But considering for example the following transformer:

    IMG_20150812_120636.jpg

    I don't understand why the lengths taken from the sketch by the solution's procedure are the following:

    For the right and left part resistance:
    [itex]R_r = R_l = \frac{(\frac{1}{2} + \frac{1}{2} + 1 ) l}{\mu A} = \frac{2 l}{\mu A}[/itex]

    For the middle part resistance:
    [itex]R_m = \frac{l}{\mu A}[/itex]

    So my question in general is: how should I measure the "l" in the general formula?
     

    Attached Files:

  2. jcsd
  3. Aug 12, 2015 #2

    Hesch

    User Avatar
    Gold Member

    Place two nodes at the top/bottom of the middle part. Call them A and B.
    The length of the path from A to B through the left and right part = 2 * l
    Through the middle part the length = l
     
  4. Aug 12, 2015 #3
    Very clear. Thanks!
     
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