Re: Is electromagnetic field theory unified?
From: Bjoern Feuerbacher (feuerbac_at_thphys.uni-heidelberg.de)
Date: 03/04/05
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Date: Fri, 04 Mar 2005 11:56:31 +0100
JM Albuquerque wrote:
> "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?
No. I claim that an electric field is induced in the vacuum.
Methinks we two are using the word "induced" with slightly
different meanings.
Hint: I use it as commonly used in physics.
[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.
We can measure a lot more than only voltage. We can measure currents,
forces, etc.
[snip irrelevant story]
> Concluding, what you measure is not the full story.
Indeed. Without a good theory, measurements don't help much.
> The electric field tells nothing about the story.
Why do you think so?
>>>>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)
And where did you get this strange formula from?
> Voltage is a potential.
Wrong. Voltage is a potential difference. I notice that you
have not explained what "potential voltage" is supposed to mean.
> dB/dt is the space distribution.
This sentence does in no way explain what "space distribution"
is supposed to mean.
> mu - magnetic permeability of the medium
>
> When you close the circuit the voltage will drop drastically,
The voltage between which points?
> which means that the electric field drops drastically.
Non sequitur.
>>>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.
Methinks you don't bother to learn what physicists actually mean
when they say "potential".
>>>The said electric field does nothing.
>>
>>Err, it exerts force on charges. Essentially by definition.
>
>
> Right.
So you admit that your claim that it "does nothing" was wrong?
> 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.
Err, charges can also be free. Ever heard of vacuum tubes, for example?
> 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.
And that's why I keep telling you that you spout nonsense.
>>>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.
Err, these equations are written down to *describe* the real world.
So why do you claim that electric fields, which are described by
the equations, are not "real"?
> The real world shows us that the amount of force depends on the
> physical properties of the copper wire loop.
What copper wire loop? We are talking about the force on test
charges.
> 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.
What on earth are you talking about here?????
Apparently we two talk about two totally different forces! You seem
to talk about something like an induction force, whereas I merely
point out that the presence of an electric field can be measured
by looking at the force on test charges.
> The electrical field defines the potential voltage V.
You still have not explained what "potential voltage" is supposed
to mean.
Actually, the electric field defines the potential Phi, and that
determines the voltage (= potential *difference*) between any
two points.
[snip more irrelevant stuff about receivers]
Bye,
Bjoern
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