In their paper "Basics of the Thermoelectric Effect with Magnetic Readout ", of February 2000, Johann H. Hinken and Yury Tavrin describe the thermoelectric eddy current and associated electromagnetic field which are produced whenever an element of one electrically conductive material is completely enclosed within another (dissimilar) electrically conductive material and subjected to a temperature gradient across its length. See:
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This effect is used in the field of non-destructive testing (NDT) in order to detect impurities or inclusions of dissimilar materials in a test piece.
Does anyone know if experiments have been carried out in order to determine whether or not this effect is reversible?
In other words, has it ever been established whether or not an external electromagnetic field of the appropriate characteristics can be applied to such an inhomogeneous test piece in order to reproduce the eddy current and associated temperature gradient?
And if not, does anyone think that this could be done?
There can not be an electromagnetic field inside a conductor.
The experiment looks for a static magnetic field.
Read the above again, this time for comprehension.
Once again, it is not an electromagnetic field, but a static magnetic field.
Electormagnetic fields can't exist inside a conductor.
Utter nonsense; the magnetic field would be caused by the current generated by the temperature gradient via the Seebeck effect.
The Seebeck effect is not reversible and in any case has nothing directly to do with magnetic fields.
Aren't you the kook that is trying to save the children from the horrors of amalgam fillings?
The same one I offered about two years ago to buy the equipment for to test your "theories" if you would do the experiments and publish the results, then went quiet for a while?
And thank you for correcting me on my (perhaps) over-liberal use of the term "electromagnetic field".
Nevertheless, I'm sure that you recognise that in spite of the fact that the effect described at:
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- may be more appropriately described as a "magnetic" field, my question regarding the reversibilty of this effect is still a pertinent one.
And in this respect I would like to ask for further clarification of your assertion that, "the magnetic field would be caused by the current generated by the temperature gradient via the Seebeck effect."
Are you not simply reasserting the effect that has already been stated here?
How does this assertion have any bearing of the question as to whether or not this same effect is reversible?
Are you saying that it would not be possible to generate a "magnetic" field of the appropriate characteristics via an alternative external source?
And if so, how do you know that it wouldn't?
And lastly, your additional assertion that, "The Seebeck effect is not reversible and in any case has nothing to do with magnetic fields", is both factually incorrect (the reverse of the Seebeck effect is the Peltier effect) and contradicts the very effect as described accurately in the paper by Hinken and Tavrin above.
Do you have any explanation for your apparent confusion?
So ridiculing me is still the only way you are able to come to terms with your own (and everyone else's) ignorance regarding the electromagnetic and thermoelectric behavior of dental amalgams is it?
Ho-hum, well let's try again.
The following is from the abstract of a report on some experimental work by Adnan H. Nayfeh, Hector Carreon, and Peter B. Nagy of the Department of Aerospace Engineering and Engineering Mechanics at the University of Cincinnati:
"Inclusions and other types of imperfections in metals can be nondestructively detected by noncontacting magnetic measurements that sense the thermoelectric currents that appear when the specimen is subjected to directional heating and cooling ........ The described analytical method can be used to optimize thermoelectric inspection procedures and to evaluate the macroscopic texture of metals from their characteristic magnetic signatures."
See:
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Do you know of any reason why it should not be possible to measure the "characteristic magnetic signature" of a typical dental amalgam?
Keith P Walsh
PS, If anyone is considering attempting to answer this question please bear in mind that according to the recognised principles of scientific understanding even if you would prefer to believe that the "characteristic magnetic signature" of a typical dental amalgam is a null one, then it would still be necessary to corroborate this preference via experimental measurement in order to establish it as fact.
And remember, a typical dental amalgam is accurately described as an inhomogeneous mixture of dissimilar metals. A cross-section of the microstructure of one such mixture can be seen at:
Over two years ago I offered to buy the test equipment to do the experiments to test your "theories" if you would do the tests and publish the results.
Mr. Walsh, One experiment is worth a thousand expert opinions. Purchase some equipment, fabricate some test samples, run the experiment. Then you will KNOW the answer to your question. Paul O.
- describes the thermoelectric eddy current and associated magnetic field which are always produced whenever an element of one electrically conductive material is completely enclosed within another electrically conductive material and is subjected to a temperature gradient across its length.
The picture at:
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- indicates that a typical dental amalgam may be accurately described as an inhomogeneous mixture of dissimilar metals in which a great many elements of electrically conductive material are all completely enclosed within a matrix of a dissimilar electrically conductive material.
Temperature gradient is ubiquitous in nature, and one might expect therefore that when a metal amalgam dental filling is subjected to a temperature gradient thermoelectric eddy currents would also circulate around the inclusions of dissimilar metals within the material, and their associated magnetic fields would be induced.
And of course establishing whether or not these magnetic fields would be significant enough to be detected outside the surface of the filling would indeed require a degree of experimental investigation.
Now, if you can use your imagination with a little more maturity than some of the other correspondents in this newsgroup appear to do, suppose I worked as a materials researcher in an electronics company and it struck me that the thermoelectric behavior of amalgams of this type might prove useful in particular electronics applications. I might then reasonably expect to find out from a professional dental materials scientist what the thermoelectric and electromagnetic properties of such materials are. And why? Well, because amalgam fillings are placed in children's teeth, and you would therefore expect that any physical behavior of the material which might present even the remotest possibility of causing interference with the neurological tissue in a patient's mouth should have been researched thoroughly before the material was accepted as being suitable for the purpose.
It is by this rationale that one arrives at the perfectly reasonable conclusion that such research should therefore have already been carried out.
But if it became apparent to me (as the electronics researcher) that no such research had ever been carried out, then I might find this odd.
I wouldn't necessarily run out into the street shouting "Save the children! Save the children!", (as some contributors appear to have imagined I actually do). I might not give a damn about any children.
But I might still logically and rationally find it odd that, in view of the fact that amalgam fillings are placed in children's teeth, it appears that there isn't anyone anywhere in the world who knows what the electromagnetic or thermoelectric properties of a typical dental amalgam are.
I have noticed that some people get upset when I point this out.
Perhaps they're the ones who should be doing something about it.
Offhand, I do not know the strength of the thermoelectric effect between the metals used to make dental amalgams.
However, the paper you cite:
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calculates the strength of the magnetic field one would expect in a copper-constantan system. (Presumably these metals are popular choices for thermocouples because the thermoelectric effect is strong for this combination.)
The answer they calculate in the paper is 20 pT (picotesla) in the plane of the current loop. This is really, really small. As they say in the paper, "only the most sensitive magnetometers have a significant chance to detect the expected magnetic field values at a proper signal to noise ratio."
I suppose this is for a 1 C temperature difference. Even if you had a 100 C temperature difference (highly unlikely inside the human mouth) the magnetic field would be only
2000 pT, or 2 nT, or 2e-9 T.
In comparison, the earth's magnetic field is about 5e-5 T. Hence, even with a 100 C temperature difference, and with a copper-constantan thermocouple, the expected magnetic field strength is more than four orders of magnitude weaker than the earth's magnetic field.
No need to ridicule you Mr. Walsh, you do it to yourself so well, no one else need step in.
I still see you as the gentleman troll AND mercury almagam induced head case spammer. Your posts are harmless and in good fun unlike others on various sci. newsgroups.
IMO the funniest reply to your last round of posts was this gem by the ascerbic Uncle Al, who posted a little over a year ago:
From: Uncle Al Organization: The Noble Krell Subject: Re: 40,000 V vs. 350 mV Date: Wed, 21 Sep 2005 15:44:25 -0700
Walsh - you are a spamming trolling idiot with a psychotic dental amalgam fixation. Have all your teeth pulled, shove them up your ass individually or in groups, then FOaD.
Your whole argument is based on the idea that the safety of dental amalgams were vetted by some sort of regulatory body that used modern testing methods. As you well know this is simply not the case. Dental amalgams is a very old technology. And the safety of the products were not fully tested (in the modern sense of the term) before they were being used by dentists all over the word.
Many years have passed and millions of people have had dental amalgam fillings with no "obvious" ill effects. Therefore, the assumption that the product is safe has been "grandfathered in".
Now you (and many other people) are challenging the assumption that amalgams are safe. I understand that. There are many examples of products that were once assumed to be safe that were later found to be harmful. So it is not unreasonable question the safety of an old product like dental amalgams.
Most people who are against the use of dental amalgams question their safety based on the fact that they contain a potentially toxic substance, mercury. You however, have followed a different path. Your argument against the use of dental amalgams boils down to this:
-The thermoelectric effect can generate small eddy currents inside dental amalgams.
-These currents generate magnetic fields that can be leave the confines of the amalgam.
-These magnetic fields are large enough and cause some sort of harmful effect.
-Some research organization (perhaps the International Society of Dental Material Scientists) should be forced to spend time and resources to study these phenomena for the good of all mankind.
Most people on this news group (myself included) disagree with your arguments. We've told you dozens of times that the amount of current generated in an amalgam due to the thermoelectric effect would be minuscule. Hence, any magnetic fields generated would also be minuscule.
But you are not convinced. So, it's time for you to stop reading papers, stop posting arguments, and stop calling for researchers to investigate your suppositions.
It's time for Keith P. Walsh to purchase some equipment, fabricate some test samples, and run some experiments.
Best of Luck, Paul D Oosterhout I work for SAIC (but I don't speak for SAIC)
Yes, I think that Uncle Al was still sore at me for having exposed his ignorance in an earlier thread.
Here's how it happened. This is from Tues, May 22 2001 (Uncle Al first, then me):
">> LOL. You should add, for the uninformed, that the thermoelectric power
-or perhaps until a dentist screws metal alloy retaining pins into the root sockets of a patient's tooth and encases the heads of the pins in mercury amalgam.
How much would one expect the thermoelectric power to matter then?"
You see, Uncle Al didn't realise that it has been regular practice for dentists to screw metal alloy retaining pins into the root sockets of patients' teeth and encase the heads of the pins in amalgam.
I invited him to explain how, as he had implied, this would "matter", but he declined the offer.
I think that ever since then Uncle Al has been inclined to fly into a childish rage at the very appearance of any of my messages in his regular newsgroups.
I suppose he must be mortified that his ignorance could have been exposed so easily.
I've dug out my own favorite of Uncle Al's "gems".
The following is part of a newsgroup message from Mati Meron, Senior Research Associate in the Center for Advanced Radiation Sources at the University of Chicago (dated Sun, Sep 5 2004).
He is addressing his reply to Uncle Al in response to Uncle Al's comments on one of my submissions to sci.physics entitled "Has Nigel Calder Got Einstein Wrong".
(first me >>, then Uncle Al >, then Mati, then Uncle Al again >, then Mati again):
*************** start*********************
What's your problem, what he posted is quite accurate.
Would you have bothered to read, you would've noticed that he says exactly what you try to say.
Mati Meron snipped-for-privacy@cars.uchicago.edu
*************** end *********************
Uncle Al had completely misread my posting (I wasn't disagreeing with Nigel Calder), and he flew into one of his childish diatribes once again (I guess it must have hurt him real bad that someone should have exposed his ignorance as easily as I had done over the amalgam thing.)
Fortunately for me on that occasion a respected research scientist, Mati Meron, stepped in to put Uncle Al straight.
So I hope you don't think that I worry too much about what Uncle Al says.
In fact I would suggest that your apparent enthralment by Uncle Al's contributions indicates a serious lack of discernment on your part.
My argument is based more fundamentally on the fact that it has been demonstrated experimentally that metal amalgam dental fillings generate electrical potentials with magnitudes of up to 350 millivolts.
You can read all about it at:
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And it appears that these electrical potentials are generally always present, because other studies have demonstrated that they quickly re-establish themselves whenever they are momentarily discharged. See:
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Apparently, some dentists (usually ones who share my concerns about amalgam fillings) routinely measure electrical potentials of this magnitude in amalgams in the mouths of their patients. (By the way, I've read all the comparisons citing static charges arising from walking across carpets which measure in thousands of volts, but I do not believe that they compare like with like. The amount of energy dissipated by the discharge of such a potential would not power a flashlight bulb for any appreciable length of time at all, whilst a battery of only a handful of volts will do the job for many hours. So I make no apology for asserting that the only scientifically accurate way to determine the nature of the dissipation of the electrical potentials generated by metal amalgam dental fillings would be to measure it.)
However, there does appear to be some confusion or lack of understanding as to exactly which physical process or processes give rise to these "amalgam potentials".
It seems that dentists are often only able to discuss the electrical behavior of amalgams in tems of "galvanic", or electrolytic, activity. But then some dentists are also taught in dental schools that as a result of "galvanic" activity, a layer of oxide forms and adheres to the surfaces of newly placed amalgams, thereby preventing any further elrectrolysis from taking place. Well I have no reason to suggest that this is not correct. But the trouble is it also appears that those dentists are then simply allowed to form their own opinion that this "explanation" alone accounts for all of the electrical behavior of dental amalgams. And it doesn't. For a start, metal oxides do not make particularly good electrical insulators, so this surface layer would not prevent electrical potentials arising as a result of physical processes other than "galvanic" activity from being dissipated to their surroundings in the form of an electrical current.
My enquiries concerning the thermoelectric (and electromagnetic) behavior of dental amalgams form only a part of my own attempt to resolve apparent contradictions which surround this subject. (I still think that the thermoelectric and electromagnetic behavior of amalgams should already have been investigated).
Nevertheless the thing that strikes me more than anything as a result of asking these questions is that it has become apparent that lots of things which ought to be known about the physical behavior and physical properties of dental amalgams aren't (or at least if they are then this knowledge is not generally available).
Metal amalgams formed by mixing grains of a metal alloy with liquid mercury at room temperature and allowing the mixture to harden were first adopted for use in restorative dentistry more than 160 years ago. This practice was quickly followed by a rise to prominence in our societies of psychiatric "medicine". It may not be obvious that these two facts are linked, or that the former may actually have had some effect in causing the latter, but then some things are not obvious until you take the trouble to find out. (I'd say that it isn't obvious that these two facts are not linked either.) But in any case the ONLY accurate and scientific way to find out is by experimental investigation.
In recent years technologists have developed extremely sensitive instruments which are able to detect neurological activity in the human body.
I would therefore suggest that, in view of the fact that it has been demonstrated experimentally that metal amalgam dental fillings generate electrical potentials with magnitudes of up to 350 millivolts, and in view of the fact that the resting potential of the human neurological synapse is only 70 millivolts, and of course in view of the fact that amalgam fillings are placed in children's teeth, experimental procedures to determine whether or not neurological function in the vicinity of teeth with amalgam fillings is measurably different from neurological function in the vicinity of teeth without them should have been carried out.
Would you not agree? (I'm sorry but I do not own the necessary equipment for carrying out these measurements myself.)
Keith P Walsh
PS, I recognise that you have tried to make your own argument as rational, intelligent and scientific as possible. But I put it to you that if you were more honest you would recognise that you are largely just making excuses for ignorances which should not exist.
Mr. Walsh, I was impressed with Muller, VanLoon, & Davidson's paper. The voltages that they measured we much higher than I would have expected. The paper clearly attributed the voltages were being generated by galvanic action.
But you have a different theory - the voltage potentials are being generated by the thermoelectric effect. I disagree.
I think that an inhomogeneous mixture of metals would make a very poor thermoelectric battery. A dental amalgam mixture would provide too many paths for the currents to flow through. In other words, your thermoelectric battery would be shorted out.
But, I could be wrong. If the emf is being generated by the thermoelectric effect, then the voltage will vary with the difference in temperature between the hot side pole and the cold side pole.
So take a crowbar to your wallet and purchase some dental amalgam material, some de-ionized water, some PTFE tubing, some gold plated contact pins, and some paraffin wax. Rent or borrow a good digital volt meter. Construct a test apparatus and then run the experiment. Prove it to us - and more importantly - prove it to yourself.
Good Luck Paul D Oosterhout I work for SAIC (but I don't speak for SAIC).
OK then Mr Oosterhout, maybe I'll get round to it sometime soon.
But I think that you are still missing a most fundamental point.
It shouldn't be possible for either you or I to be able to think of any experiment to investigate any aspect of the electrical behavior of dental amalgams which hasn't already been carried out. (Especially one which can be done as easily as your shopping list implies.)
And if you're not sure why this is so, then I shall explain it to you again.
Metal amalgam dental fillings are placed in children's teeth.
Now, it has been demonstrated experimentally that amalgam fillings generate electrical potentials with magnitudes of up to 350 millivolts. And the resting potential of the human neurological synapse is only 70 millivolts.
Therefore I say that experimental procedures to determine whether or not the electrical potentials generated by amalgam fillings are able to dissipate electrical energy through the nerves in people's heads should already have been carried out.
And if they haven't then the obligation to carry out such investigations lies not primarily with myself, but with those people who advocate the continued use of amalgam fillings on the grounds (presumably) that these fillings do not dissipate any electrical energy through the nerves in people's heads as a result of the electrical potentials that they undoubtedly generate.
In a previous posting you implied that any concern about adverse effects resulting from the electrical behavior of amalgam fillings was uniquely mine.
You were wrong.
The following are quotes from the websites of two qualified, practising and apparently prosperous dental surgeons.
1) From the website of US dentist Paul Genung:
"Having read this far, you are probably thinking this article is primarily concerned with mercury toxicity. The toxicity, however, is not as severe a problem (for most people) as the electrical currents flowing in our mouths. Although they are rarely recognized, these currents cause far more problems than the mercury itself."
- see:
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(You'll need to find Google's cached version now, search for - genung "a battery in your mouth".)
2) From the website of UK dentist Dr Philip Wander:
"Nevertheless, as potentially damaging as mercury in the mouth is the electricity itself. When testing teeth for electrical effects, I have seen momentary sparks of up to one volt - enough to light a small torch or flashlight. It's worth remembering that the currents generated by amalgams are formed very close to the brain, which ordinarily operated at far lower potentials (only a few millivolts). The brain lies only a few millietres from the jaw bone, where the roots of the teeth are inserted, just on the other side of the thin cranial bone and the meninges (the three membranes enveloping the brain and spinal cord). This kind of current can cause mental dysfunction, which I often find in clinical practice."
- see:
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Before you presume that I've been suckered by such claims, let me explain to you that there are generally three different ways in which one can respond to claims like this - only one of which is the "scientific" response. The three ways are:
1) Dismiss the claims out of hand because you don't like the sound of them.
2) Believe tham without question.
3) Carry out experimental investigations to see if you can detect any evidence for their being valid.
(ok so category number one might be "because you consider them incorrect", but even then you'd be just guessing.)
Did you spot the scientific response?
It's number three.
I think that most, if not all of the people who have disagreed with me on this question have gone immediately for option 1 (unscientific!).
Worse still, they appear to presume that I've gone for option 2 (not true!).
I would in fact going for the (only) scientific option, which is to suggest that any scientific investigation which is reasonably possible to carry out in order to investigate these claims should be carried out. However I do not agree that it is my sole responsibility to do it.
And on that particular point here's something that you might like to consider. The claims published on the above websites regarding the effects of the electrical behavior of amalgam fillings flagrantly contradict the advice that professional bodies such as the American and British dental associations give with regard to the "safety" of amalgam.
But there doesn't seem to be anything that these bodies are able to do to censure these dentists' claims.
If you yourself were able to carry out tests which showed that to the best of our ability we are not able to detect any dissipation of electrical energy through the nerves in people's heads as a resullt of amalgam potentials, then those dental associations might be extremely grateful to you. (But only of course if you are able to tell them what they want to hear.)
Why not have a go?
You might just beat me to it.
Keith P Walsh
By the way, did you check out Dr Philip Wander's list of celebrity patients. They include some of the best known stars ever to play for one of the world's greatest soccer clubs - Manchester United. Eric Cantona, Ryan Giggs, and even David Beckham. Big role models? Or just suckers?
Not a snownball's chance in hell it would ever happen.
Not likely.
Utter, babbling, nonsense.
People that know the science involved generally feel no need to do a pointless experiment.
Here comes the bullshit...
So what?
Metal amalgam dental fillings are place in adults's teeth and animal teeth and have been for about a hundred years or so.
Non-related nonsense.
More nonsense.
Nope, only you and other kooks with no understanding of basic science are concerned.
I offered to buy you the test equipment to do the experiments to test your kook theories over two years ago as long as you did the experiments and published the results.
You never took me up on the offer.
You don't care about children.
You don't care about any possible effects of dental amalgam.
All you care about is posting your nonsense over and over again.
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