Re: EM Induction - A conceptual question

[Chuck Britton <britton@NCSSM.EDU>]

except along the side that is IN and PARALLEL to the B field. THIS is
where the non-zero contribution comes in. Carl seems to have it
right. There  must be a fringing field to cancel it.

DOES this fringing field affect the original question? I don't THINK so.




At  12:02 PM -0400  on  4/17/02,  John S. Denker   wrote
> Chuck Britton wrote:
> >  ok. I am considering a totally STATIC situation.  (A MAJOR shift in
> >  calculations!)
>
> OK, new question requires new answer;  see below.
>
> >  And my question concerns CURRENT that is wrapped enclosed by an
> >  amperian loop. The line integral of B around this loop is s'possed to
> >  equal the current passing through the loop.
> >
> >  THIS consideration makes me scratch my head in responce to:
> >
> >    >The original question described a piecewise-uniform B-field.
> >  >  >Uniform in one area and zero in another.  There's nothing
> >  >  >mutually-exclusive or inconsistent or unphysical about this.
> >
> >  the line integral of B around the given (amperian) loop is NOT zero
> >  but there is also NO current 'penetrating' the loop!
>
> You gotta read the fine print.  The integral in question
> is the integral of
>         B dot dS
>           ^^^
> where dS is an element of the loop.  It's not |B| times |dS| or
> anything like that.
>
> In the specified geometry, B is perpendicular to dS, so
> the integral is zero, and there's no problem.

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Chuck Britton                                   Education is what is left when
britton@ncssm.edu                               you have forgotten everything
North Carolina School of Science & Math         you learned in school.
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