Re: Is electromagnetic field theory unified?

From: JM Albuquerque (jm.aREM.OVE_at_sapo.pt)
Date: 03/03/05 

Date: Thu, 3 Mar 2005 15:07:44 -0000

"Bjoern Feuerbacher" <feuerbac@thphys.uni-heidelberg.de> escreveu na
mensagem news:d06s1s$3le$1@news.urz.uni-heidelberg.de...
> JM Albuquerque wrote:
> > "PD" <pdraper@yahoo.com> escreveu na mensagem
> > news:1109347942.522594.100980@o13g2000cwo.googlegroups.com...
> >
>
> [snip]
>
> >>As a result of this increasing magnet field, there is an induced
> >>electric field.
> >
> >
> > Yes if the magnetic field is increasing and if you have something
> > to be induced.
>
> That "something" is the electric field. No wire or anything like
> that required. Works pretty well in a vacuum.

Nonsense.
You claim the vacuum is induced by means of an electric field?

> > According to Faraday's Law there is an induced electric field.
> > No problem.
>
> Nice that we agree on that.
>
>
> [snip]
>
>
> >>I can test for this field by placing a *stationary* charge in the gap
> >>and observing the force on the charge. Whether I put the charge there
> >>or not does not affect the existence of the field.
> >
> >
> > Here I do have some difficulties since charge is an artefact with no
> > physical reality (the same as the field lines),
>
> We can *measure* charge, so how can you claim that it has no physical
> reality?

Actually you can measure voltage but that won't tell you much of the story.
For instance when I was a kid I had lots of problems with my motorbike.
Some times the engine dies and after looking for a gas problem the
next step is to look for an electric problem. The spark plug can by bad,
or there is no voltage. So one call the first stupid guy around that is
looking at you and ask him to hold the spark plug wire for you. Them
you kick hard on the starter and look if the guy gives a jump or not.
If he jumps you know you got those 50,000 Volts in the wire.
The same 50,000 Volts can be present on the National grid wires,
but for sure nobody will ask nobody to hold those wires.

Concluding, what you measure is not the full story.
The electric field tells nothing about the story.

> [snip]
>
>
> >>Mathematically, the source of the electric field loops is from the
> >>contribution to the curl of E from dB/dt (Faraday's law). There is no
> >>divergence of E from a closed loop, which is why no such term appears
> >>in the divergence equation for E (Gauss's law).
> >>
> >>Perhaps you did not know that closed-loop electric fields without
> >>charged sources can occur?
> >
> >
> > I believe they are the space distribution of potential voltage.
>
> And what exactly do you mean with "potential voltage" and with
> "space distribution" here?

Voltage = mu * inductance * dB/dt (open circuit)

Voltage is a potential.
dB/dt is the space distribution.
mu - magnetic permeability of the medium

When you close the circuit the voltage will drop drastically, which
means that the electric field drops drastically.

> > But they are only a potential, like is a rock on the top of a table
> > is in respect to the gravitic field.
>
> Methinks you should learn what "potential" means in physics. You keep
> using the term with its meaning in ordinary, laymen language.

The above was correct.

> > The said electric field does nothing.
>
> Err, it exerts force on charges. Essentially by definition.

Right. Nevertheless you only have those charges if you place
a nearby a loop of wire where the charges can flow, or charges
can accumulate in the electrical terminals of the said loop of wire.
And that's why I keep telling you that "the receiver does all the
difference". With no receiver, no charges, no force, no induction,
nothing.

> > Nevertheless its mathematic
> > formulation tell us the amount of force and the amount of current that
> > we can get if a given closed loop of copper wire, with a given
> > electrical resistance and a given self inductance, is placed nearby.
>
> Why do you insist that this is only a mathematical formulation, but
> not reality?

Because that's all you can get from equations written on a paper.
The real world shows us that the amount of force depends on the
physical properties of the copper wire loop.
Actually the said force depends on the physical number of turns
of the copper wire, the physical area enclosed by the loops,
the wire physical resistance to the flow of charges and the
physical medium around which the loop of wires are wounded.
Concluding you can have the amount of force you want just by
controlling the loop impedance.

The electrical field defines the potential voltage V.
The physical characteristics of the receiver define the impedance Z.
Being R the electrical resistance a I the current (flow of charges):
Ohm's Laws tell you that V=Z I
The force will be proportional to R I^2 (the dissipated power)

You can have no force, some force, or a large force.
The reality changes depending on the receiver.
Can't you understand that?

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