Talk:Thermoelectric effect

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Thermoelectric effect has had a peer review by Wikipedia editors which is now archived. It may contain ideas you can use to improve this article.

This page has been cited as a source by a media organization. The citation is in:

"Utah Teens Invent Better Air Conditioner", Slashdot, July 21, 2005. (details)

[edit] This article conflicts with itself

Joule heating has not been reversed, but is theoretically possible under the laws of thermodynamics ...and... The first term ρ J² is simply the Joule heating, which is not reversible

[edit] Planning major re-write

I've been working on a paper regarding thermoelectricity for a class, and it's taken me a while to get the factors straightened out in my own head. At this point, I think I can present the information fairly clearly. The peer review page doesn't seem to be there still, but I'll definitely be looking over the material here for suggestions on directions to take.

Beakdan 16:52, 15 November 2007 (UTC)

[edit] Dead External Link

I've commented out the link to "Two Utah teens invented a durable, clean, efficient air conditioner based on this principle" because the page has been removed. It is however available in the google cache, so I'm not sure if whoever added that would like to do something about it to keep it around, or not. -Scott Dial 02:08, 3 September 2005 (UTC)

The google cache is now gone too.

[edit] EMF

How is the EMF generated and where does the engery for this come from?

It's described in the article. The hot and cold charged particles diffuse through the metal, but they move at different rates, leading to a net movement of charge from one end to the other. The energy comes from the applied heat difference. - Omegatron 03:14, August 2, 2005 (UTC)

Maybe the wording of this could be improved; Also is it required that there be two junctions? I find this point confusing, at one point it states that the EMF is due to the junction, where later on in the article it states that the EMF is due to the flow of heat, presumably if it is due to the flow of heat, no junctions are needed, not to mention two. mickpc Also what is the relationship between the electropotential of the different metals (or semiconductors) and the EMF produced? mickpc

When a single bar of metal has a heat difference between the two ends, a voltage will appear between the two ends as well. If you connect two bars of the same metal in a loop, you will get no net current because the voltages generated in each will cancel out. If you connect two dissimilar metals in a loop and keep a temperature difference between the two junctions, the net speed of particle diffusion in each will be different and a net current will flow. That's how I understand it, anyway. - Omegatron 14:33, August 3, 2005 (UTC)

Any ideas on the difference between say the primary thermocouple material and the conducting wire so that the conducting wire does not effectivly cancel the EMF of the primary thermocouple? mickpc

Ok I have read my text again and it specifically says that the EMF is due to the junction not the tempriture difference in the main thermocouple material. So which is right? mickpc

It is an extremely common misconception that the voltage is either a function of the junction between disimilar metals or is developed across the junction. It is NOT a junction effect at all and there is typically no voltage across the juntion. It is an effect along the length of the conductor (a voltage gradient) that is a funtion of the thermal gradient (The Thomson/Seebeck effect). The only reason you need dissimilar materials is that otherwise the voltage gradients along two conductors would be identical and you would not be able to measure or untilize any voltage differential a the ends of the conductor pair. Perhaps someone can take the time to explain that better and add an illustration. Here is one reference that provides some explanation of what I am trying to explain, http://www.sensoray.com/support/tcapp.htm

I will try to find another good reference.67.134.13.42 (talk) —Preceding comment was added at 01:22, 9 May 2008 (UTC)

[edit] Year of discovery

The first line of the description is incorrect. It was first discovered by Thomas Johann Seebeck in 1821. Not by Peltier in 1884. Seebeck was not even alive anymore in 1884. He died in 1881!

I saw two pages that said 1821, but this page [1] says 1823. I intend to add more to this article. Omegatron

[edit] Direction of electron flow

"Electrons flow from the hot end to the cold end."

I am not so sure this is true. I think it depends on the type of conductors, so I am taking it out for now. Feel free to put it back if you know it is true. Omegatron

It is true in metals. Apparently not in semiconductors, in which "positive particles" - holes - are free to flow. I have expanded on it a lot now, though. (Great... now I'm talking to myself...) - Omegatron

[edit] Redirect thermoelectricity to here

Just to make sure people know, I redirected thermoelectricity to here, although there might be other forms besides the peltier-seebeck kind?

I changed this back to a non-redirect, since there is also vacuum tube thermoelectricity. - Omegatron

[edit] Diagram check

Please double-check the polarity of my voltmeter in the diagram. I think it is right, but i am not terribly qualified. - Omegatron

[edit] What came first?

Did Seebeck discover the voltage difference first or the current loop/compass first? - Omegatron 17:09, Apr 2, 2004 (UTC)

I believe Seebeck THOUGHT he had discovered a thermo-magnetic effect, since he used two dissimilar metal wires joined at each end and forming a loop, in close proximity to a compass. Therefore I would suggest, from my limited reading on the subject, it was the current effect that he initially noticed.

I took the liberty to remove the word "is" from immediately before an expression because the subject of the expression was stated immediately before the expression, that is;

"If a current density J is passed through a homogeneous conductor, heat production per unit volume is

   q =......",

changed to;

"If a current density J is passed through a homogeneous conductor, heat production per unit volume;

   q =......"

I do not like the term 'thermopower' as an alternative for the Seebeck constant, since the Seebeck constant is measured in Volts and is in reference to the potential so I would assume is an open circuit quantity, no power would therefore be produced. I do realize that this is a term in general use and I would like to make it clear that I am not critisising the article, just putting an opinion forward for discussion. —Preceding unsigned comment added by 81.1.123.201 (talk) 22:05, 1 January 2008 (UTC)

[edit] Integrals

$V = \int_{T_1}^{T_2} (S_B - S_A) \, dT$

I would like to show that these are functions of T, but

$V = \int_{T_1}^{T_2} (S_B(T) - S_A(T)) \, dT$

$V = \int_{T_1}^{T_2} (S_{BT} - S_{AT}) \, dT$

$V = \int_{T_1}^{T_2} (S_{B\,T} - S_{A\,T}) \, dT$

$V = \int_{T_1}^{T_2} (S_{B_T} - S_{A_T}) \, dT$

are all ugly. - Omegatron 20:25, Jul 5, 2004 (UTC)

[edit] Phonon drag picture

I forgot which one it was but, why did you take off the change carrier diffusion/phonon drag picture? lol, I would not have read that paragraph or two if the picture didn't catch my attention. --Mac Davis 11:13, 9 Jan 2005 (UTC)

The Seebeck effect in a bar of metal, showing the flow of hot electrons only.

The flame and the metal bar? I don't think it is accurate, after thinking about it. The first explanation I heard said that hot electrons would diffuse through the metal bar, which made sense to me, and explained the basics of how heat could generate electric current. So I drew that picture. Then I read more into it, and the cold electrons diffuse in the opposite direction in roughly equal quantities. The imbalance between the two is what actually causes the net electric current, and is caused by the phonon drag and scattering. So, since the picture only shows hot electrons diffusing, it's not accurate. I could make a more accurate one if you could describe what it should look like. I don't really understand phonons and have no idea how to draw phonon drag. :-) - Omegatron 18:42, Jan 9, 2005 (UTC)

[edit] Pyroelectricity

Is pyroelectricity the same phenomenon as the seebeck effect?

I don't think so. One is in metals and one is in crystals. But I am no expert. - Omegatron 00:15, Feb 12, 2005 (UTC)

I think Omegatron is talking about piezoelectricity. The article states materials with one usually have the other. This article is about two dissimilar materials (metals) creating current between hot and cold ends, but pyroelectricity is about one material developing an electric potential when heated. Is that what you guys get from the pyroelectricity article?

[edit] Why not to make it in three pages?

I think that this page can be put in three:

Like you can see all those pages are already here, and making Peltier-Seebeck effect page in three part will just ask to remove the redirect and put part of article in. In fact main matter of having on page insted of three is that links to the others languages are falses, and that make bots from others' wiki copying bad links and put mess in link between the wikis. So I think that is a good thing to make this page become three. Please say what you think about it? Oliviosu 17:10, 10 July 2005 (UTC)

I combined the three articles into one a while ago, since they are all variations on the same effect. I think they should stay together. - Omegatron 19:41, July 10, 2005 (UTC)

Not true. "The three thermoelectric phenomena are the Seebeck, Peltier and Thomson effects. Of these only the Seebeck effect converts thermal energy to electric energy and results in the thermocouple voltage used in thermometry." CRC Press. Measurement, Instrumentation, and Sensors Handbook.

There's also no mention of absolute Seebeck effect. —Preceding unsigned comment added by Quincy8Boy (talk • contribs) 14:03, 2 October 2007 (UTC)

[edit] Links to the others wikis

For this time I set this page as if it was Peltier effect page by deleting links to Thermoelectricity that are aleredy in Thermoelectricity page, I also set nl language link to the nl peltier page insted of nl seebeck page because all links to other wiki are to the peltier effect pages and making that allow bot to work without putting mess. Oliviosu 17:28, 10 July 2005 (UTC)

[edit] Slashdot Warning

An article [2] on the Peltier effect was posted to slashdot.org recently. There are no links to this page, but I think that should account for the reoccurring vandalism.

Wow! My first chance to see a revert happen right before my eyes. (I pulled up the history and edit pages and it had already been reverted).--Lzygenius 05:36, 21 July 2005 (UTC)

May it be suggested that another revert and lock be put on the article until things settle down? Maybe a programmic lock on stuff that gets referred off of Slashdot for at least a week? --STrRedWolf 05:41, 21 July 2005 (UTC)

Yeah, I've protected it now. There's no problem reverting all the slashdot-kids, but having it open is just adding too much nonsense to the page history at the moment. Shanes 05:44, 21 July 2005 (UTC)

Maybe there should be a {{slashdotted}} template. - Omegatron 06:09, July 21, 2005 (UTC)

I don't particulary like that template myself. To me it looks more likely to be encouraging slashdot-kids to live up to the reputation of setting their mark on every site being linked to. "Yeah, we slashdotted it!!!!112!". That's why I was reluctant to protect the page myself in the first place. I hate giving in to vandals. Anyway, now that the current and protected version is exactly the same as the version before the slashdot-link, is it really neccesary to warn people about the acuracy of it? Shanes 07:05, 21 July 2005 (UTC)

I agree with Shanes. It seems to play into the vandal mentality. Better to just quietly resist, I think. --InformationalAnarchist 07:21, 21 July 2005 (UTC)

Yeah. Well, anyway, I'll unprotect it now. The worst should be over now. Shanes 08:29, 21 July 2005 (UTC)

Me too, I think there should be enough responsible Wikipedians directed here by the slashdot article at the same time as the vandals. I for one come and check Wikipedia articles that are linked to by Slashdot. Usually someone beats me to it and the vandalism is already reverted :-) I did once suggest protecting Slashdot-linked articles, but was shouted down and for good reason I think. — PhilHibbs | talk 09:01, 21 July 2005 (UTC)

I agree that protecting the page is a bad idea. We want to convert them, if possible, and they won't be converted if they can't edit the page. :-) I think the current wording of the slashdot template could be changed. - Omegatron 14:05, July 21, 2005 (UTC)

[edit] Superconductors

From the article on 20050904, Superconductors have zero thermopower, and can be used to make thermocouples. Should that read, "... and can't be used to make thermocouples." It seems to me that with no voltage drop, there can be no temperature drop either. If it means that they can be used in conjunction with other materials to make thermocouples, then I still think it's a bit confusing.

[edit] Elite Language

can somebody translate the article to common english? the language used is CRAP. the author of the article should ask him/herself: for what kind of audience am i writing?! answer: OH, I AM WRITING IT FOR EVERYONE ON THIS PLANET FROM THE MOST DUMB TO THE MOST INTELLIGENT! noone wants to decipher an article before one is able to read it.

Examples? — Omegatron 20:31, September 11, 2005 (UTC)

The language seems to require a basic high school science education. I do not think that is unreasonable.

I agreee, the language should be changed

Examples? — Omegatron 18:32, 2 March 2007 (UTC)

[edit] Seebeck-Peltier-Thomson: Who Discovered What

The Wikipedia article describing the Seebeck effect (see above) suggests that it was Thomas Johann Seebeck who discovered that "a voltage existed between two ends of a metal bar when a temperature gradient existed in the bar".

However, it is more likely the case that Seebeck never actually knew that this fact was true. The explanation for this is as follows:

Textbooks often propose that there are only three fundamental thermoelectric effects, however it is in fact possible to describe four.

The four thermoelectric effects, listed in chronological order of their discovery, are:

Effect 1 - If two different conductors are joined and the two junctions are maintained at different temperatures, an electromotive force is developed in the circuit.

Effect 2 - If a current flows in a circuit consisting of two different conductors then one of the junctions is heated and the other is cooled.

Effect 3 - When a temperature difference exists between two points in a single electrical conductor an electrical potential is established between the points.

Effect 4 - If a current passes through a conductor in which a temperature gradient exists, this current causes a flow of heat from one part to the other.

These effects are obviously very closely related. Indeed, each of them represents a reversible effect whereby effects 1 and 2 are the reverse of each other and, similarly, effects 3 and 4 are the reverse of each other.

Thomas Johann Seebeck first identified Effect 1 in 1821. He spent the rest of his scientific career measuring the size of this effect for different pairs of dissimilar conductors in contact with each other. Seebeck died in 1831.

In 1834 Jean Charles Athanase Peltier first identified Effect 2, the reverse of Effect 1. Peltier died in 1845.

Significantly later (around 1854-1855), William Thomson first deduced and demonstrated BOTH of the effects numbered 3 and 4.

Starling and Woodall describe part of Thomson's contribution thus (from "Physics", Longmans, 1950):

"He [Thomson] suggested that there must be other electromotive forces in the circuit and that these exist in the metals themselves, acting between the parts of any one metal at different temperatures. This was found to be correct. Thus if two points in the metal differ in temperature by the amount dT, the electromotive force in this element of the metal is s.dT. The quantity s is called the Thomson coefficient. It is taken to be positive when directed from points of lower to points of higher temperature."

As a result of the above, the four thermoelectric effects are correctly attributed the following names:

Effect 1 is the Seebeck effect.

Effect 2 is the Peltier effect - and is correctly identified as the reverse of the Seebeck effect.

Effects 3 and 4 together comprise both "directions" of the Thomson effect.

Some recent sources restrict the definition of the Thomson effect to that of Effect 4 only, and this may be either the cause or the result of a further tendency to prefer that the definition of the Seebeck effect may be satisfied by that of Effect 3 (with the possible consequence that Effect 1 is rendered anonymous).

Again, it is clear that the relationship between Effect 1 and Effect 3 must be a very close one.

However, it has been demonstrated that during his lifetime Thomas Johann Seebeck could not ever have been explicitly aware of Effect 3.

Furthermore, in the effect which Seebeck spent the greater part of his career measuring, when the junctions between the dissimilar metals are maintained at different temperatures a net electromotive force exists in the circuit which causes a current to flow around it. Such a circuit cannot be constructed with a single conductor, and therefore the definition of Effect 3 may not serve as an adequate explanation for the Seebeck effect.

It is not necessarily erroneous to say that there are only three thermoelectric effects, so long as it is understood that one of them, the Thomson effect, comprises both "directions" of the reversible effect; and that one of the others, the Seebeck effect, is the reverse of the Peltier effect and requires at least two dissimilar conductors to produce.

References: "Physics", Starling and Woodall, Longmans, 1950; "The Penguin Dictionary of Physics", Revised for the third edition by J P Cullerne B.Sc. D.Phil.

Keith P Walsh

Add this to the article! (With references, of course.) Very good info. — Omegatron 14:12, 7 December 2005 (UTC)

Ok, you literally added this section to the article. :-) That's not quite what I meant. I meant to modify the article's descriptions about each effect in light of your discoveries, with a reference for each fact changed. You're not going to append a paragraph onto the end of the article; you're going to edit the actual article to reflect your changes. Also, we don't include self-references like "The Wikipedia article above". — Omegatron 21:13, 22 January 2006 (UTC)

Thank you for your advice.

The statement in the article that Seebeck "... found that a voltage existed between two ends of a metal bar when a temperature gradient dT existed in the bar." is inaccurate.

Perhaps you might like to assume responsibility for correcting it yourself.

Keith P Walsh

Il you wish (and if you speak french), you can find a detailed description of the thermoelectric effects discoveries there : fr:Thermoélectricité (this article is a brief summary of my thesis introduction). And I can confirm that the statement that Seebeck "... found that a voltage existed between two ends of a metal bar when a temperature gradient dT existed in the bar." is inaccurate : Seebeck found a voltage at the jonctions of of two dissimilar metals. Sincerely, David Berardan 11:00, 27 January 2006 (UTC)

[edit] Good Article nomination has failed

The Good article nomination for Thermoelectric effect has failed, for the following reason(s):

The lead section should be expanded to summarise more of the article's content.
The article may be too technical for a general audience to understand.

Also, what's the relevance of the Patents section? It's not much use at the moment as a list with no context. I'd suggest removing the see-also section; relevant links are already in the text. And you might consider removing sub-section headings in 'external links' as it bloats the TOC somewhat unnecessarily. Worldtraveller 09:57, 14 June 2006 (UTC)

I agree about the patents - those aren't even particularly notable among the hundreds of TE-related patents. The Hansell patent isn't even for a TE device - it's a thermionic converter (?!). I'm taking that whole section out. If anybody wants to put it back in, please select only patents that are (a) relevant to the topic and (b) unusually significant, and add some commentary to justify it. Tarchon 20:08, 30 October 2007 (UTC)

Shame that this article is considered too technical for a general audience to understand! As a general reader I found it brilliant, clearly expressed and utterly fascinating. Maybe the world itself should be rewritten in a less complex form, so that some grumpy lazy people don't have to work at understanding it.

[edit] Peltier effect

I think this needs to point out in order to work the two metals need to have significatly different work functions. Otherwise the current itself will cause more heating than the cold end can compensate for.

So point it out. This is a wiki. — Omegatron 17:10, 9 December 2006 (UTC)

Uh... I did... I did this from memory and I was hoping someone with a reference available can confirm and thus make it more reliable. —The preceding unsigned comment was added by 12.10.127.58 (talk) 18:27, 15 December 2006 (UTC).

[edit] Thermal differentials

Hello, I am new, but trying to be bold. I thought that "thermal" made a lot more sense than "heat" in the first sentence of the article since heat is not a quantity in the static sense, only as a flow. The old Caloric theory would say otherwise but it has of course been superceded. I think that the passage both makes more technical sense this way and the high school science educated reader can still understand it. Feel free to revert and discuss, I won't be offended! Wes Hermann 02:37, 5 December 2006 (UTC)

I've amended it to "temperature differences" - differentials and differences aren't the same thing, and TE is all about temperature differences. I think this is part of the language that other people were complaining about. "Differential" as a noun is a technical term from mathematics that's sometimes incorrectly used as a generic synonym for "difference". Tarchon 18:38, 30 October 2007 (UTC)

[edit] Joule Heating ≠ Thermoelectricity

I made some big changes in the intro, and the biggest one is that Joule heating is no longer identified as being a TE effect. I know it's related, and if you want to parse "thermoelectric" it seems like JH would be part of it (this is a semantic error that formerly plagued the thermoelectricity article), but in common scientific parlance, Joule heating is not usually considered a TE effect. It's extremely common to draw a dichotomy between thermoelectric and Joule/Ohmic behavior in the technical literature. As the article notes, reversibility is a key difference here. Tarchon 19:57, 30 October 2007 (UTC)

S.Morkisch (talk) 21:22, 10 April 2008 (UTC) Hello, The Link to related sites below contains a link which cannot be loaded: http://www.sii.co.jp/info/eg/thermic_main.html

Kind regards, Sebastian Morkisch —Preceding unsigned comment added by S.Morkisch (talk • contribs) 21:20, 10 April 2008 (UTC)

[edit] Image Problem

I think the image "Thermoelectric Cooler Diagram.svg" is wrong, because it shows current coming out of the positive terminal of a battery and going into the negative terminal. Charges should be moving out from the negative and into the positive terminal. —Preceding unsigned comment added by 151.196.139.68 (talk) 23:05, 14 May 2008 (UTC)

The direction of an electric current is defined as the direction in which positive charge carriers would flow. This is the opposite of the direction negative charge carriers (electrons) actually move. The direction of the current in the diagram is therefore correct (from the positive terminal, to the negative). Any introductory text in physics will confirm this. O. Prytz (talk) 20:04, 21 May 2008 (UTC)