# Electromagnetism formula question

Discussion in 'Homework Help' started by Kai Jie, Sep 2, 2016.

1. ### Kai Jie Thread Starter New Member

Jul 11, 2016
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Is the magnetic path length(L) equal to the mean circumference, 50π mm?
If yes, then for question (c), should I skip it and go to question(d)&(e) to calculate (R) and (Fm), then only answer (c)?

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2. ### MrAl Well-Known Member

Jun 17, 2014
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Hello,

The magnetic path length is taken to be the mean circumference if the cross sectional area is constant and the material is uniform throughout.

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3. ### wayneh Expert

Sep 9, 2010
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Agreed. Think of it as the average length of all the various field lines. I suppose for an irregular cross section it would be the area-weighted average length. So if most of the material is at the outer perimeter, the average field line would be longer than if most of the cross section is at the inner edge.

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4. ### Kai Jie Thread Starter New Member

Jul 11, 2016
3
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Thanks for the help guys.