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Author Topic: Can an experiment discern between electric currents and electromagnetic waves?  (Read 8431 times)

Offline sorincosofret

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Electric currents and electromagnetic waves hypothetic experiment

Proposed experiment
For the experiment are necessary two sources of alternate current and two sources of electromagnetic waves, with possibility to modify the amplitude and the frequency.
There is a difficulty to find a medium with equal conductivity for alternate current and for electromagnetic waves, but letís suppose that such medium exists (therefore the experiment is considered hypothetical).
For the simplicity of experiment letís consider that the arrangements from fig. 1.



Figure 1. Alternate currents and electromagnetic waves source arrangements

The experimenter can vary the intensity (I) and the frequency (f) of electric currents or electromagnetic waves sources, and the ammeter in the first circuit, respectively a detector of electromagnetic radiation in second circuit detects the consequences.
For the simplicity of analysis letís consider that in first circuit I1=I2 and f1 ≠f2; the ammeter will register an intensity obtained as result of vector combination of both intensity.
In case of electromagnetic waves sources, choosing the same intensities I1í  = I2í and
f1í ≠f2í  there will be no vector addition of these intensity.

Actual and proposed explanation

Both electric currents and electromagnetic waves are considered as making part from the same class of physical phenomena and they are treated unitary using the same lows of electromagnetism, more precisely Maxwell equations.
The first mismatch occurs when a medium with same conductivity for electric current and for electromagnetic waves is searched.
The second mismatch regards the different composition of two electric current and two electromagnetic waves. There is a similitude of two electromagnetic waves addition like two currents only when their frequencies are the same (interference phenomena). It is necessary to highlight ,,a similitudeĒ because as will be described in the book, even in these case at a detailed analysis there are differences. Generally speaking, electromagnetic waves do not add like two currents.
In the proposed theory electric currents and electromagnetic waves are different phenomena. Beside the different physical mechanism which is laying at basis of electric current and electromagnetic wave production, their effects are different too. Consequently there are necessary different equation and different physical models for these concepts. In proposed theory the Maxwell equations are ruled out for both phenomena description.





 

Online Bored chemist

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I think I'm begining to understand what the phrase "not even wrong" means.
"There is a difficulty to find a medium with equal conductivity for alternate current and for electromagnetic waves, but letís suppose that such medium exists"
I have a much better idea- let's not make that weird supposition.
 

Offline sorincosofret

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I'm happy if my post touch your ,,correct attitude or aptitude of seeing".
No comment on the experiment per se?

Does two electromagnetic waves add like two electric currents?
 

lyner

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Sorin. Here we go again.
Conductivity is conductivity. It may vary with frequency but it is part of the complex quantity called admittance. The quadrature quantity is susceptance.

This is good old classical EM theory and there are so many books about it you could build yourself a classroom with them. Try reading a few of the better ones. Go through the Maths and they will give you the answers to all these questions of yours.

Currents and fields all add vectorially. Superposition is a principle which works so how can you say "they don't add up in the same way"? For two sources of the same frequency, in your EM version, you can expect the fields to add up, according to the relative amplitudes, phases and Field vectors. How else do you expect transmitting antennae (and the two slits experiment) exhibit interference?
You can't have a changing current without an EM wave being there and you can't have a varying EM field without an induced emf in a conductor. The only worthwhile exercise you can do is to go through the Equations (Maxwell's) and see if you get the same answer as they do in the books. When (and if) your conclusions are at variance - check your sums. If they still disagree, then you have done very well.
There is no point in challenging stuff as well established as EM theory without being prepared to do the calculations.

If you really want to do something useful, you can explain how E and H vectors are cophase in free EM waves but in quadrature in guided waves. What happens as a wave is launched?
You seem to have plenty of energy - direct it at a worthwhile question.
 

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"No comment on the experiment per se?"
Here's a comment.
The experiment isn't possible, it never was and it never will be. As a concept it is devoid of any meaning.
 

Offline sorincosofret

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Currents and fields all add vectorially. Superposition is a principle which works so how can you say "they don't add up in the same way"? For two sources of the same frequency, in your EM version, you can expect the fields to add up, according to the relative amplitudes, phases and Field vectors.

Currents and fields add vectorially in case of two currents with different intensities and frequencies flowing in the same conductor. TRUE

Currents and fields add vectorially in case of two electromagnetic waves  with different intensities and frequencies flowing in the same medium. FALSE
In this case, you will not be able to catch a radio program, because you will catch a resultant of composed individual waves.
Electromagnetic waves does not follow the same rules of composition like electric currents.

It is necessary for some people to start reading some books about logic. The first book was written 2000 years ago by Aristotle. There are described some simple rules of discriminating between a false or real concept and how can be made practically. 
 

lyner

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In this case, you will not be able to catch a radio program, because you will catch a resultant of composed individual waves.
That's exactly what you do get  going down the antenna feed. The receiver filters out, in the frequency domain, the wanted signal from the unwanted signal. At any one point in space there can be only one Electric Field Vector and One Magnetic Field Vector. They will be varying according to the Sum of all waves passing, in magnitude and direction. (That's what a vector is, I believe)

If they don't add up in a linear fashion (vectorially) then you would get cross modulation between two signals in space. This does happen in a non linear medium, of course, when the medium itself carries some of the energy but, in space, it doesn't. You need MegaWatt levels of transmitted power to even get a hint of this effect in the ionosphere.

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It is necessary for some people to start reading some books about logic.
I think it's necessary for some people to start reading some books about Electromagnetic Theory, sorin.
 

Offline Pumblechook

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Luxembourg effect.  Some engineers doubt it exists.  HARRP is studying it. 
 

lyner

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Luxembourg effect.  Some engineers doubt it exists.  HARRP is studying it. 
Interesting comment. When I was 'into' ionospheric propagation I seem to remember reading some pretty well substantiated reports. It was a while ago and the results may have been explained another way.
Here's an old reference:
http://resources.metapress.com/pdf-preview.axd?code=n742r02748572315&size=large
 

Offline Pumblechook

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I think it was observed some decades ago and not been heard since??
I can't say with all my short wave and medium long wave listening and short wave operating that I have ever heard it.  It has been thought that people were mistaken.  Radio Luxembourg (208 Metres) for instance was so strong at times across Europe that it was simply overloading receivers. It may be that some transmitters were a bit dirty..spurii...or 'wide' due to overmodulation. That article refers to 'intense' heating of the ionosphere by powerful transmitters which (I think) is nonsense.  Even HAARP with it Megawatts of ERP firing straight up has  only a small effect compared to the UV from the Sun. 

« Last Edit: 29/10/2008 23:02:35 by Pumblechook »
 

Offline Pumblechook

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If the nearly 4000 MW ERP HAARP in Alaska can only slighlty tickle the ionosphere what could much lower power transmitters possibly do?

From a site...

----HAARP might be powerful by our modest standards, but a single bolt of lightning is far more powerful. HAARP isn't doing anything that our own sun doesn't do on a daily basis -- and causes nowhere near the disturbance created in the atmosphere by a geomagnetic storm -- nor can it come close to reproducing the myriad of atmospheric effects in the ionosphere all the time. For instance, did you know that several layers of the ionosphere practically disappear at night? HAARP can't even produce artificial aurora up there in the home of the Northern Lights -- at least not ones that are visible to the naked eye -- because it can't generate anywhere near that kind of energy. Compared to Mother Nature, our efforts are puny, indeed. ----

HAARP has been blamed for Space Shuttle disasters, hurricanes, even causing women to miscarry as far away as Tokyo.  Not doubt someone will blame it for the  financial meltdown.
« Last Edit: 29/10/2008 23:25:07 by Pumblechook »
 

lyner

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You could be right, although the main detectable effect would be cross modulation of the strong signal onto the weaker or the generation of intermod products. Harmonic radiation would be very hard to distinguish / isolate because of all the other causes. The same effects will occur in receivers but proper RF filtering would eliminate all but the genuine article. It also depends upon your location with respect to the Earth's magnetic field, I believe.
I wasn't aware that it was a 'heating' effect. That would not be likely; non linearity would be a much better explanation.

On the subject of high power transmissions, there was a large log periodic HF radar array on the East Coast at Orfordness which used very high power pulses to see over the horizon (cold war). It was reputed to have caused flash fires in the rigging of distant passing ships.
The system was dismantled years ago but the whole setup was incredibly James Bond. It never worked very well - partly, I heard, because the insulators in the antenna (hundreds of them) would break down and need replacement.
I designed an mf transmitting array which is still on the same site and can be seen, easily, on Google Earth. It consists of six monopoles, in the form of two yagi arrays, beamed at Eastern Europe. My own personal Wall of China. I don't know if it is still operational.
 

Offline Pumblechook

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I only mentioned 'heating' because it was in your link and heating is mentioned WRT to HAARP, probably incorrectly.  I am not too clued up on phyisics ..how the ionoisation actually takes place..  But as far  as I know it is a slow effect.  Ionisation dies  slowly after the source of the ionisation is removed.  Meteors passing through the I-sphere leave a trail of ionisation which lasts a matter of seconds.  So  changes in ionisation can't be fast enough to follow audio frequencies.  It would have to be some non-linear effect in the I-sphere causing intermodulation but you would expect harmonics and higher order products to be produced rather the audio from one transmiision appearing in the background of another.  One theory seemed to be that the powerful TX was causing night-time ionoisation of the D layer and increasing its absorption.  It is day-time ionisation of the D-layer and its blocking effect which causes the Medium Band to be essentially ground wave only during daylight. I presume it is the E-layer which is the reflective layer for MF frequencies which remains sufficiently ionised for hours after sunset.  I read the effect was noticed on a transmission in the 30s...Received in Holland from Switzerland with Luxembourg half way.  But the LX TX would have used a vertical radiator so not firing much straight up????   It remains Teslarian..  An effect claimed to have occured a long time ago which nobody can explain or reproduce.   Like Marconi claiming to have bridged the Atlantic in 1901 on about 800 kHz during the day with a very crude receiver...doesn't add up.  You couldn't do it now with modern gear.

I can't even seen HAARP with its massive ERP causing flashing over at any great distance at all really.

There are still areas of radio propagation we can't explain like summer Sporadic E and TEP.

I have just seen an edition of Coast and they showed Cobra Mist at Orford Ness.  There are claims that it didn't work because the USSR used disguised trawlers pumping out interference.
« Last Edit: 30/10/2008 14:24:11 by Pumblechook »
 

lyner

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The ionisation is caused by cosmic rays. There are free electrons floating around the low density gas until they recombine. This constitutes a conducting medium for RF - like a metal plate - and you get reflection (simple model). The displacement / oscillation of the electrons (the ions are too massive to oscillate far so they don't count) is proportional to the field and so it is a linear medium. If the displacement is too great (like the mean free path, I guess) then it is no longer just proportional and the non linearity occurs. This is where A sin(x) + B sin(y) give you components like sin(x+y) and (A+B)sin(x); intermodulation and cross modulation.

That is far too simplified and what you actually get is a gradient of complex refractive index which causes total internal reflection. It is very frequency dependent (higher frequencies can go straight through) and, where the layer is more dense, you get absorption of lower frequencies. Hence, the Max and Min usable frequencies at any particular time.

As the electrons go ' up and down' they are affected by the Earth's magnetic field and can move in circles, causing cross polarisation too. There's no end to the complications.

I always get cross when people like sorin post such garbage without any acknowledgement for the generations of workers who have sorted out loads and loads of this stuff and backed it up with so much experimental data. He comes along with a Van der Graaf generator and a couple of multimeters and reckons he has solved it all. I really respect so much of the work which started off with excellent theoretical rigour and has mostly been shown later to be spot on by experiment.
« Last Edit: 30/10/2008 16:31:05 by sophiecentaur »
 

Offline Soul Surfer

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I fail to see what all this discussion is about.  It is fundamental from Maxwells equations that electromagnetic waves to not propagate within a material with a significant amount of conductivity they just attenuate and decay exponentially.  they will however propagate in the surface layers in the form of the well known skin effect.  For good conductors the skin effect is very shallow even at frequencies as low as 50Hz and for any large currents that are expected to change at a significant rate it is important to use multiple stranded consductors that are insulated from each other.

This clearly sows that the originating question in this thread is totally and fundamentally flawed rising from a lack of understanding of how electromagnetism actually works as is all that questioners work.
 

Offline sorincosofret

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The Maxwell equations are valid ( in actual description) for direct currents too. Does a direct current flow only at the surface of conductor?
The skin effect is valid for alternate currents at higher frequency.
The skin effect does not manifest to a electromagnetic wave. In case skin effect will be valid for electromagnetic wave, your antenna should be stacked on Earth or must be raised in ionosphere.
The post had taken a non sens direction, but I'm not interested to correct it. For me it\s important the existence of the post and I will try to make comments as little as possible .
« Last Edit: 03/11/2008 07:11:09 by sorincosofret »
 

lyner

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SS: there are many media which can't be characterised as 'good conductors' - glass or water for instance. The em waves propagate through all media to some degree. The complex refractive index is the term which effectively describes how the waves pass through / interact with the medium. One way of looking at it is to think of the molecules bending and stretching as the fields change - absorbing some energy at the same time. The 'springiness' is associated with the dielectric constant (reducing the wavespeed) and the energy loss is associated with the resistive element.
The wave is not necessarily evanescent to any significant degree.Of course it is with conductors and sometimes at dielectric boundaries - as with the forward wave when there is total internal reflection.

The categories are pretty arbitrary for some media.
 

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"The post had taken a non sens direction"
Ab initio.
 

Offline Soul Surfer

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sophiecentaur   I was not talking about dielectric materials (which frequently allow electromagnetic waves to propagate through them quite well) in my previous reply but materials that conduct electricity well like metals and some that conduct moderately well like semiconductors or other resistive materials. water is an anomalous material for radio frequencies because of its polar and polymeric structure It has a very high dielectric constant unlike glass  and even tiny quantities if ionic salts in it cause it to conduct significantly.
« Last Edit: 04/11/2008 00:17:40 by Soul Surfer »
 

lyner

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It is fundamental from Maxwells equations that electromagnetic waves to not propagate within a material with a significant amount of conductivity they just attenuate and decay exponentially.
The still propagate - just not very far.
MF transmissions 'propagate', too,  over the ground but attenuate eventually.

It's just a matter of degree, surely. There are media which fall between two conveniently described categories of behaviour - 'dielectric' and 'conducting'.   The ionosphere is a good example. Waves will follow the laws according to the properties of the medium.
Non linearity is a further issue - very applicable to situations with high power lasers, for instance.

But this is an 'aside' as BC points out.
« Last Edit: 05/11/2008 10:57:47 by sophiecentaur »
 

lyner

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sorin
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Does a direct current flow only at the surface of conductor?
Are you trying for a reductio ad absurdum argument here?
Current never flows just 'at the surface' - there is always a skin depth.
There is no such thing as a true direct current - it will have a finite period of flow (it's been switched on and off for the 'experiment' and the reactive properties of the circuit will impose finite rise and fall times). That implies a non-zero frequency content. That implies a finite skin depth. Nothing absurd at all.
 

Offline Pumblechook

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I think skin depth is inverse prop' to the sq rt of the frequency so at very low frequencies the depth tends towards infinitity so will be much deeper than the diameter of any  practical conductor. 
 

Offline sorincosofret

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It is premature to discuss about alternate and continuous currents. For the moment actual theory does not provide why a alternate current tends to flow on the surface of the conductor (with a certain depth in the conductor volume) and why this depth is decreasing with frequency.
In fact for actual theory is quite indifferent if a electron is oscillating with 50 Hz or with 50 MHz.
In a second in both situation the electron should make 50 or 50 M oscillations around a equilibrium position. In the same time in absence of ,,alternate" current a electron run 1 mm in a second. So from macroscopic point of view a oscillation with 50 Hz or with 50 MHz should have the same effects on the electron movement. More precisely the electron does not follows the electric field variation. In this case how the alternate current propagate in the conductor?
 

lyner

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Of course an electron does not follow the em field exactly - there is a  phase lag as the electron needs to accelerate and this takes time. Is that new to you? Have you done any work on the behaviour of oscillating masses under periodic forces?

It really would be a good idea if you actually read something substantial about this and didn't try to become an expert by skim-reading some simplified text. You claim to have understood and rejected what advanced texts have to say but you ask questions which demonstrate that you haven't understood them.
Have you not read anything about skin depth? What 'actual theory' have you been reading?
Is your knowledge only skin deep?
« Last Edit: 06/11/2008 23:19:59 by sophiecentaur »
 

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