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

• To: syedmhusain@xxxxxxxxxxx, juergen.rauscher@xxxxxx,si-list@xxxxxxxxxxxxx
• Date: Thu, 29 Jan 2004 18:08:25 -0800 (PST)

```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.

--- 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
> >
> >
>
------------------------------------------------------------------
> > To unsubscribe from si-list:
> > si-list-request@xxxxxxxxxxxxx with 'unsubscribe'
> in the Subject field
> >
> go to:
> > http://www.freelists.org/webpage/si-list
> >
> > For help:
> > si-list-request@xxxxxxxxxxxxx with 'help' in the
> Subject field
> >
> > List technical documents are available at:
> >                 http://www.si-list.org
> >
> > List archives are viewable at:
> > http://www.freelists.org/archives/si-list
> > or at our remote archives:
> > http://groups.yahoo.com/group/si-list/messages
> > Old (prior to June 6, 2001) list archives are
> viewable at:
> >   http://www.qsl.net/wb6tpu
> >
> >
>
>
------------------------------------------------------------------
> To unsubscribe from si-list:
> si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in
> the Subject field
>
> to:
> http://www.freelists.org/webpage/si-list
>
> For help:
> si-list-request@xxxxxxxxxxxxx with 'help' in the
> Subject field
>
> List technical documents are available at:
>                 http://www.si-list.org
>
> List archives are viewable at:
>               http://www.freelists.org/archives/si-list
> or at our remote archives:
>               http://groups.yahoo.com/group/si-list/messages
> Old (prior to June 6, 2001) list archives are
> viewable at:
>               http://www.qsl.net/wb6tpu
>
>

__________________________________
Do you Yahoo!?
Yahoo! SiteBuilder - Free web site building tool. Try it!
http://webhosting.yahoo.com/ps/sb/
------------------------------------------------------------------
To unsubscribe from si-list:
si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field

http://www.freelists.org/webpage/si-list

For help:
si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field

List technical documents are available at:
http://www.si-list.org

List archives are viewable at:
http://www.freelists.org/archives/si-list
or at our remote archives:
http://groups.yahoo.com/group/si-list/messages
Old (prior to June 6, 2001) list archives are viewable at:
http://www.qsl.net/wb6tpu

```