Is there a magnetic "dead zone" somewhere between the two poles of a coil?

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Offline djc0245

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Principle:    When using a coil for induction of a longitudinal magnetic field, the appropriate field strength selection is based upon the following formula:

                       I - Amperes required
     KD               K - 45,000 amperes turns
I = ----              L - Length of specimen
     NL               D - Diameter of Specimen (if solid)
                       N - Number of turns/wraps in coil

Effective area:   18 inches, 9 in. from center of coil/wrap both directions.
Given results:    Polarization of aligned electrons in specimen, N at one end, S at the opposite end.
Verified by:      Flux field leakage, demonstrated by lines of force at each end of specimen.

Inquiry:  Due to the lack of uniformity in most specimens' perimeter profile, Isn't there an existence of a neutrality point (maybe very narrow - almost indiscernible) in the center of the coil between the poles? Since a measurable reduction of applied field strength exists there? And shouldn't there be an established theoretical or industrial standard of identifying the neutral point, as a "Dead Zone"? Or for validity, at the least establish the practice of repositioning specimens?

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« Last Edit: 09/06/2008 10:25:07 by chris »


Offline Bored chemist

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Good question and I don't know the answer.
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The actual system description is a bit vague and I can't be sure what the actual question is  but my answer to the question as I understand it is:
I don't think there is any likelihood of a 'neutral point' (do you mean 'null')
The field might be a bit non-uniform along the axis of the coil due to  the finite spacing between the turns  but Ampere's Law, I think, precludes having nulls .
Perhaps a diagram would help to make the question more clear.


Offline Soul Surfer

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No.  The magnetic field runs substantially uniformly along the axis of the coil.  outside the coil the field loops back substantially like a bar magnet.  Magnetic "poles" in this context are rather ill defined areas in the vicinity of the ends of the coil.
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Offline daveshorts

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A field line is the route that an unnattached N pole with no mass would follow, so it would go straight from the North end of the coil to the south end very rapidly.


But if you had two North poles near each other then there would be a 'dead zone' of no field between them.


Offline Atomic-S

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The field inside a coil is nowhere zero.


Offline qazibasit

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good numerical and a real nice effort.
"There is never too late to make a change".