Re: Catt anomaly?

[Brian Whatcott <inet@INTELLISYS.NET>]

At 05:46 AM 11/26/01, Antti Savinainen wrote:

> >> when a pulse is sent down a simple cable (e.g. coaxial),
> >> the edge of the electric field is moving at [local] c.
>
> ...
> What is interesting to me is that according to Catt two experts in
> electromagnetism gave different answers to his question. Catt writes
> (<http://www.electromagnetism.demon.co.uk/w99anbk2.htm>):
>
> "Consider the case when the battery and lamp are connected
> by two very long
> parallel wires, their length being 300,000 kilometres. When the switch is
> closed, current will
> flow immediately into the front end of the wires, but the lamp will not light
> for the first second. A wave front travels forward between the wires at the
> speed of light,
> reaching the lamp after one second. This wave front comprises electric
> current,
> magnetic field, electric charge and electric field. Negative charge appears on
> the surface
> of the bottom wire. All of this is agreed by all experts...."
>
> The question asked by the Catt Anomaly is where this charge on the bottom
> conductor comes from, and the answers given to this elementary question are
> contradictory, with the academic establishment split down the middle.
>  Half of the academics, led by McEwan, say that the charge comes from the
> battery to the
> west and
> reaches its proper place along the bottom conductor without having to
> travel at
> the speed of light. The other half of the academics, led by Pepper, say
> that it
> is
> impossible for the charge to come from the west because it would have to
> travel
> at the speed of light, resulting in the charge having infinite mass. Pepper
> says that at the
> moment when charge is needed to help the wave front along, it comes to the
> surface of the wire from inside the wire, travelling at right angles to the
> direction of the
> wave front."
>
> I guess that a surface charge theory (see for instance Chabay & Sherwood in
> <http://cil.andrew.cmu.edu/rchabay_extra/mi_docs.html>) can account very fast
> (but not c in vacuum) propagation of electric field in a conductor. But how?
>
> Regards,
>
> Antti Savinainen


If I recall, Catt is a maverick, who is in fact addressing a weakness
in physics teaching in this general area, leading to amusing nonsenses
like the instantaneous transmission of a pulse down a long line -
an instance that was discussed on this list within the last year or two.

 It will be helpful to simplify the Catt puzzle to a ladder configuration
of a delay line
- namely four series inductors in each of two lines, connected by three
parallel capacitors, and terminated in a resistance of the value of the
characteristic impedence of the line.

He asks effectively: when a battery is connected to one end of a delay
line of this kind - where does the charge in the final capacitor come from?
Though electromagnetic transmission is inherently relativistic, I expect
one could provide a satifying description of an energy transfer between
magnetic
 and electric modes, without taking oneself too seriously?





Brian Whatcott
  Altus OK                      Eureka!