sci.physics.electromag

On Tue, 4 Mar 2008, xray4abc wrote:

> I think now that it does.
> Simple experiments, performed by Oleg D. Jefimenko and others
> have shown electric field-lines around the wiring of some electric
> circuits.
> (see references in 'The electric force of a current" by A.K.T. Assis
> and
> J.A.Hernandes ).
> These force-field lines are different from the ones that would exist
> if
> no current is flowing through the circuit.

I wouldn't put it that way around, but would instead say that an electric
field is needed to create an electric current.

Ch2 in Assis has some nice figures showing the kind of surface charge
distributions one would expect. He is correct to point out that there must
be a component of the Poynting vector parallel to the wire, as well as the
more commonly mentioned perpendicular component of the Poynting vector. If
there were not, how could energy travel from the power supply to outside
some part of the wire in order to move into it?

> Interestingly, O.d. Jefimenko does not consider the current as a
> source of electric field.
> He mentions 3 sources of an electric field : 1. charge density
> 2.the
> time derivative of charge density
> 3.the
> time derivative of current density J
> My question is meant for those who are familiar with the mentioned
> authors'
> approach to the theory of electromagnetism.

It's just a case of 1, the surface charge density (again, well-illustrated
in Assis). Current in a resistive circuit doesn't just flow by itself.

--
Timo Nieminen - Home page: http://www.physics.uq.edu.au/people/nieminen/
E-prints: http://eprint.uq.edu.au/view/person/Nieminen,_Timo_A..html
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