[SI-LIST] Re: Partial Inductance/Vector Potential

Syed:

how about commenting on this counter example to your
last statement:

A=Log(r) - does not vanish at infinity, yet the
magnetic field H=curl(A)=1/r still vanishes at
infinity.  :-))

The above dependencies actually describe the exact
case of a field around an infinite wire (carrying
current) In this case the entire wire contributes to
A. However, if you consider just a short segment of
the wire - like it's done in the concept of partial
inductance - then A~1/r and H~1/r^2 (as it should be
according to Bio-Savara law.) 

One more comment: the vector potential can be offset
at infinity from zero to anything you'd like via gauge
transformation. E&M field is gauge-invariant by
nature, which has to do with charge conservation).
Therefore, there is nothing profound in choosing A to
be zero at infinity; Rather, it's often a convenient
choice.  

-Vadim Heyfitch

--- Syed Husain <syedmhusain@xxxxxxxxxxx> wrote:
> Hi Juergen;
> 
> It simply means that at an infinite distance from
> the conductor, the
> magnetic field strength drops to zero.
> 
> Syed M. Husain
> 
> 
> ----- Original Message ----- 
> From: "Juergen Rauscher" <juergen.rauscher@xxxxxx>
> To: <si-list@xxxxxxxxxxxxx>
> Sent: Wednesday, January 28, 2004 1:21 AM
> Subject: [SI-LIST] Partial Inductance/Vector
> Potential
> 
> 
> > Hi all,
> >
> > Ruehli relates a partial inductance to the
> magnetic flux which extends
> > from a conductor filament to somewhere near
> infinity. This magnetic flux
> > is limited by boundaries starting at the end
> points of the conductor
> > filament to infinity. The magnetic flux can now be
> calculated with a
> > contour integral around the loop. Therefore the
> vector potential at
> > infinity is set to zero. What is the physical
> meaning or algebraic
> > justification for setting the vector potential to
> zero?
> >
> > Any hint is appreciated.
> >
> > Regards,
> > Juergen
> >
> >
>
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