Re: Permittivity and the Poynting vector

From: Paul B. Andersen (paul.b.andersen_at_deletethishia.no)
Date: 12/19/04 

Date: Sun, 19 Dec 2004 22:22:18 +0100

jahn wrote:
> "Paul B. Andersen" <paul.b.andersen@deletethishia.no> wrote in message news:cpuk55$h4a$1@dolly.uninett.no...
>
>>jahn wrote:
>>
>>>"Paul B. Andersen" <paul.b.andersen@deletethishia.no> wrote in message news:cps4ja$3fb$1@dolly.uninett.no...
>>>
>>>
>>>>jahn wrote:
>>>>
>>>>
>>>>>"Androcles" <dummy@dummy.net> wrote in message news:g06wd.31883$tg2.21582@fe1.news.blueyonder.co.uk...
>>>>>
>>>>>
>>>>>
>>>>>>"jahn" <susysewnshow@yahoo.com.au> wrote in message
>>>>>>news:32bod1F3k6a9aU1@individual.net...
>>>>>>
>>>>>>
>>>>>>
>>>>>>>Exerpt:
>>>>>>><<
>>>>>>>The Lorentz Force equation, is missing a force term,
>>>>>>>which is proportional to the rate of change, in e
>>>>>>>lectromagnetic momentum density, carried by a
>>>>>>>poynting vector-flux (E x B). Abruptly pulsed
>>>>>>>crossed-field, that is non-radiating, is proposed to
>>>>>>>interact with the vacuum medium, creating an
>>>>>>>action-reaction push, which can be used for transportation.
>>>>>>>
>>>>>>>E = electric field, B = magnetic field. A 1980,
>>>>>>>University of Toronto experiment, showed that a
>>>>>>>poynting vector for static fields, that causes motional
>>>>>>>force, is a fact. Electromagnetic fields contain mass and
>>>>>>>can store momentum, which can be used to generate
>>>>>>>inertial reaction forces. The use of separate electric and
>>>>>>>magnetic radio waves, are useful in this process. If used
>>>>>>>with a cavity-mode resonator, thrust is developed.
>>>>>>>It must be configured and pulsed.
>>>>>>>
>>>>>>>The missing force term, in the Lorentz Force equation,
>>>>>>>involves the energy momentum stored in an electromagnetic
>>>>>>>field. Force always involves action and reaction. Mass in
>>>>>>>motion is momentum. The product of mass = mass x velocity.
>>>>>>>An impulse is created during a time interval. A net external
>>>>>>>force causes acceleration. Force x Time = the change in
>>>>>>>time x momentum.
>>>>>>>
>>>>>>>
>>>>>>>http://www.utahspace.org/special/electric_spacecraft.html
>>>>>>>
>>>>>>>Exerpt:
>>>>>>><<
>>>>>>>The Poynting vector and power flux density.
>>>>>>>The units of electric field strength E are volts/metre, and
>>>>>>>the units of magnetic field strength H are amps/metre.
>>>>>>>Thus the product (E times H) has units
>>>>>>>(volts amps)/(square metre) or watts per square metre.
>>>>>>>A quantity having these units is called a "power flux density".
>>>>>>>We pose the question, "under what conditions does a product
>>>>>>>of an electric field strength, a magnetic field strength and
>>>>>>>an area represent a real power flow?"
>>>>>>>
>>>>>>>The traditional answer to this question is that the Poynting
>>>>>>>vector S = E x H is the vector product of the E vector and
>>>>>>>the H vector; it has dimensions watts/(sq metre) and is in
>>>>>>>a direction at right angles to the plane containing the
>>>>>>>E and H vectors, and can be interpreted as a local power
>>>>>>>flow at right angles to the EH plane, proportional to the area
>>>>>>>of the element of surface times the E field strength times the
>>>>>>>H field strength times sin(the angle between E and H).
>>>>>>>
>>>>>>>This interpretation is very suspect. >>
>>>>>>>http://www.ee.surrey.ac.uk/Personal/D.Jefferies/poynting.html
>>>>>>>
>>>>>>>---------
>>>>>>>As for experimental evidence, it IS interesting to note that
>>>>>>>that the VLTI http://www.eso.org/projects/vlti/
>>>>>>>has been catching the same photon with all four telescopes
>>>>>>>for some time now, yet the exciting 1980 University of
>>>>>>>Toronto experiment seems to have escaped the almost
>>>>>>>all-seeing web.
>>>>>>>
>>>>>>>Sue...
>>>>>>
>>>>>>Ok... so what conclusions do you draw?
>>>>>>Androcles.
>>>>>>
>>>>>
>>>>>You may be aware that the correct way
>>>>>to add the speed of an emitter and the light it emits, can
>>>>>on ocassion be the source of some lively debate on this
>>>>>NG ;-)
>>>>>Of course, the real issue is whether "space-time" or
>>>>>"ether" can actually exist. The discussion usually proceeds
>>>>>adnausium along the lines of hypothetical additive
>>>>>velocites without much consideration of
>>>>>possible other ways to prove or dispove the existance.
>>>>>
>>>>>Sometimes things are easier to see if you simply turn them
>>>>>90 degrees. So I am suggesting that the VLTI is living proof
>>>>>of the second papers paradigm and against the first paper's
>>>>>paradigm. Free-space permeablility plays an important role
>>>>>in interpreting the Poynting vector in either case, but only
>>>>>the second case (Jefferies) offers substantial experimental support.
>>>>>http://scienceworld.wolfram.com/physics/PoyntingFlux.html
>>>>>
>>>>>Free space has by it's very nature, (lack of nature ? ) the
>>>>>ability to separate charges but lacks any theoretical or
>>>>>demonstrable mechanism for the wide band storage
>>>>>of magnetic flux that we associate with dielectric materials.
>>>>>
>>>>>Sue...
>>>>
>>>>What is actually the problem?
>>>
>>>
>>>You'll have no problem with this because you're
>>>accepting of any of any absurbdity that is
>>>based on your beliefs. Just make up a
>>>new word, Quadrality perhaps ?
>>
>>Evasive as always, eh?
>>
>>
>>>>What do you mean by "the first paper's paradigm",
>>>>and how is that opposed to "the second paper's paradigm"?
>>>>
>>>>I find "the first paper" to be bordering to meaningless
>>>>babble. Mostly it is so imprecise that you can't tell what
>>>>is right and what is wrong. But much of it is definitely wrong.
>>>>("The Lorentz force equation is missing a force term". Phooey! )
>>>>
>>>>The "second paper", is, as far as I can see,
>>>>only stating conventional physics.
>>>>
>>>>I would sum the whole thing up thus:
>>>>Poynting's theorem of 1884 is correct.
>>>>But Poynting never said that Poynting's vector
>>>>is "the local power flow", even if it under
>>>>certain conditions seems reasonable to interpret
>>>>it as such. It is easy to find examples where
>>>>this interpretation yields complete nonsense.
>>>>It is also easy to find examples where this interpretation
>>>>make perfect sense. (Even for static fields.)
>>>>But use Poynting's vector as it was supposed to be
>>>>used in Pointing's theorem, and the result will
>>>>always be correct.
>>>>
>>>>But what is it you find proven by the VLTI?
>>
>>No answer?
>>You keep referring to the VLTI as if its proves something,
>>but you have never stated what you think it proves.
>>
>>
>>>>And exactly what did the "1980 University of Toronto experiment"
>>>>show that you find so remarkable?
>>>
>>>
>>>I don't find it remakable that "ether proving" papers
>>>disappear. They do it all the time.
>>>See if you can still find the HTML of Ashby's paper
>>>with this:
>>> site:relativity.livingreviews.org ashby "gravitational redshift" gps
>>>http://www.google.com/search?hl=en&lr=&q=+site%3Arelativity.livingreviews.org+ashby+%22gravitational+redshift%22+gps&btnG=Search
>>
>>Is this:
>>http://relativity.livingreviews.org/Articles/lrr-2003-1/index.html
>>an "ether proving" paper which has disappeared?
>>
>>Evasive as always, eh?
>>Never answer a question, right?
>>
>>
>>>>Do you have a reference where the experiment is described?
>>>
>>>
>>>Bill Hobba posted something related but I don't know
>>>if it's the same.
>>
>>In other words, you don't know what you are talking about.
>>You state that the "1980 Toronto University experiment"
>>is "exiting", but you don't know what the experiment is.
>>
>>
>>>>The description in "the first paper" is so vague and imprecise
>>>>that it says nothing.
>>>>"that a poynting vector for static fields,
>>>> that causes motional force, is a fact."
>>>>may be trivially true or horribly wrong according to
>>>>conventional physics.
>>>
>>>
>>>The second paper say's it's use may be horribly wrong.
>>
>>No. Not necessarily. The description is far too vague
>>to tell if it is right or wrong.
>>You see, stationary crossing E and H fields may very well
>>cause a force on a body, and any force has the potential
>>of causing motion.
>>
>>A concrete example:
>>Imagine a DC-source with voltage V connected to
>>a resistor R via a coax cable. Let the characteristic
>>impedance of the cable be R. (Not necessary, but convenient.)
>>Let the length of the cable be d.
>>Let the dielectricum be air (or vacuum).
>>
>>
>> --- I-> ---
>> | |--------------| |
>> | V |<-F F->| R |
>> | |--------------| |
>> --- ---
>> source coax load
>>
>>We have a static voltage V on the cable, and a constant
>>current I = V/R. In the coax there is a static
>>crossing E and H field.
>>
>>Everything seems static, but there is a continuous
>>EM "wave" propagating from the source to the load.
>>This becomes apparent if you imagine a short voltage
>>pulse in stead of a constant voltage. The pulse will
>>propagate from the source to the load at the speed c.
>>Now imagine the pulse getting very long.
>>It will still propagate. (The pulse front went
>>from the source to the load yesterday when we switched
>>the voltage on, the trailing edge will follow tomorrow,
>>when we switch it off.)
>>
>>If we apply Poynting's theorem on a closed surface
>>enclosing the load, Poynting's vector will be different
>>from zero only where the coax goes through the surface.
>>So according to Poynting's theorem, the power flowing
>>into the volume enclosed by the surface will be
>>Pointing's vector within the cable integrated over
>>the cross area of the cable. This integration isn't
>>very hard to do, but this is an awkward medium so
>>I won't bother to go through the math in detail.
>>But the H-field is given by the current I, and
>>the E-field by the voltage V. The integral of
>>Poynting's vector over the cross area of the cable
>>will be U*I.
>>So we can conclude that according to Poynting's
>>theorem, the power flowing into the load is U*I.
>>Which should surprise no one. :-)
>>
>>But we asked for the force.
>>The momentum of the EM-field within the cable
>>is DXB integrated over the volume of the cable.
>>Since D=e*E and B=u*H, we now know that DXB integrated
>>over the cross area must be U*I*e*u = U*I/c^2.
>>Since the fields are the same everywhere along the length
>>of the cable, the momentum of the field in the cable
>>will be: U*I*d/c^2.
>>The force on the load is dP/dt, and since P is static,
>>this will be equal to the momentum of the volume divided
>>by the time it takes for the volume to be absorbed by
>>the load. The latter time is obviously d/c.
>>Thus:
>> F = (U*I*d/c^2)/(d/c) = U*I/c.
>>
>>An equivalent analysis of the source will yield
>>the same force on the source. (Oppsite direction.)
>>
>>So there is a force U*I/c stretching the cable.
>>
>>If we made the cable telescopic, we would have motion.
>>(But the force is extremely small for all reasonable
>>values of V and I.)
>>
>>
>>>I suppose "conventional physics" is what a slim
>>>majority on a committee says it is so you can apply
>>>at your pleasure.
>>
>>By "conventional physics" I simply mean the physics
>>used by physicists as opposed to the magic used by cranks.
>>
>>But I still wonder what your point was.
>>You never state it, do you?
>>
>>Paul
>
>
> With the transmission line there is no question about
> the permeabiliy and permittivity. It is determined
> primarily by the spacing of materials and it is easily
> measured.

I note with interest that you do not comment on
the point we discussed, namely "can a stationary
crossed H and E field excert a force on a body."
It can.

> Jefferies' point is that we may be in error
> to make assumptions about free space just on the
> basis of energy and current density, particularly when
> free space is non conductive and non magnetic.
>
> Considering the many cases where E Plane energy
> predominates and few if any where H Plane energy
> predominates (far field), I think he has a point.

Your statements are always so vague that they don't
say much.

I think Jefferson's point was rather that if you use
Poynting's theorem properly, you will be right.

If you put the enclosing surface around your antenna,
never mind how close, you will by integrating the normal
component of Pointing's vector over that surface get
the power transmitted by the antenna.
(You will have to average over at least one period
to get the average power, of course.)
This will work even in the near field.

Why make a mystery of this?
There are none.

>
> e0 and u0 are based on the ether for which there is
> no proof.
>
> Sue...

Maxwell's equations were "based on the ether
of which there are no proof."
But Maxwell's equations are extremely well confirmed,
and are doing very well with no ether.

What IS your point?
That Maxwell's equations are wrong?

Paul

Relevant Pages

  • Re: Permittivity and the Poynting vector
    ... > We have a static voltage V on the cable, ... > pulse in stead of a constant voltage. ... > propagate from the source to the load at the speed c. ... This integration isn't ...
    (sci.physics.relativity)
  • Re: Permittivity and the Poynting vector
    ... >>only stating conventional physics. ... We have a static voltage V on the cable, ... EM "wave" propagating from the source to the load. ... This integration isn't ...
    (sci.physics.relativity)
  • Re: High voltage switch using IGBTs
    ... Does the pulse width ever need to change? ... Does the output voltage need to change? ... What kind of load is it? ... You can have a single big power supply, ...
    (sci.electronics.design)
  • Re: Another DC motor question
    ... > later to control the motor average current, ... > stalling torque of the motor so if driving a variable load, ... > Another method I would like to try is to allow the voltage to reach the ... many model railway pulse controllers sense the DC ...
    (sci.electronics.design)
  • Re: Will Radio Engineering be QMs worst nightmare?
    ... See what kind of voltage gets produced by 150 watts ... I am thinking of an amplifier that is turned on with no load. ... > don't increase because the load resistance changes. ... What kind of amp. ...
    (sci.physics)