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"Nanotubes"

Removed from the article:

In conformance with the known law of conservation of energy, a plot of the negative differential resistance region of a component cannot normally pass through the origin.
More recently however, Professor Deborah Chung at the University of Buffalo has discovered a composite configuration of carbon nanotubes which actually does exhibit a negative differential resistance region throughout its entire plot, which does indeed pass though the origin. Professor Chung's device could thus be considered a negative static resistor.

What's the special case that prevents this from being a perpetual motion machine?

This is a bit strange. I'm fairly sure I can build a simple circuit that exhibits negative resistance (differential or static) at the origin. Of course, it needs a power supply, so it's not really violating conservation of energy. Madhu 22:06, 4 Mar 2005 (UTC)
I looked into this, and the Chung experiment was so obviously flawed that I am not surprised that it quietly disappeared from the news. I imagine that Buffalo University and Ms Chung were so embarrassed when they realised their error that they bought up all copies of their press releases and burnt them. As an act of mercy, I have just removed the reference from our article. Just look at this photo (on this page of some free energy nut's website), but prepare for the outbreak of at least a wry smile. In case the error isn't obvious, let me explain.
1 (The Short Explanation). To measure the resistance of something, you have to pass a current into one point on the thing and out of another point, and measure the voltage between the same two points.
2 (The Long Explanation). Refer to the photo linked above. You should be looking at two bundles of carbon fibres placed at right-angles to each other and squashed together where they cross. The four points of the cross are labelled A, B, C and D. The carbon fibres have some resistance from end to end, and there is also some conductance between the two bundles (if there isn't, then you should have put more effort into tightening up the vice in the preparation stage of the experiment). When the current source is switched on, there is a voltage gradient between points A and C, with A more positive than C. Now try to answer the question: "which two points of the current path is the voltmeter connected across?" The answer is: "anybody's guess", because the terminals B and D are connected through untidy bundles of fibres to some undefined point or collection of points in the crossover area. The geometry of this setup is such that D might be positive with respect to B, or it might be negative, depending on which fibres got squashed most tightly together. It seems that in this case D is more strongly connected to A, making it positive, and B is more strongly connected to D, making it negative. Since the experimenter has chosen to connect the positive end of his voltmeter to B, he gets a negative voltage. In conclusion, the "resistance" you are measuring is not really a resistance, but the ratio of some voltage across two points to some current flowing between two other points, and its sign and magnitude are no more meaningful than random numbers.
If anybody doubts that the original experiment could have been as simple as this reconstruction, see the original paper here. Note the proximity of the submission date to the 1st of April. --Heron 21:11, 5 August 2005 (UTC)
Given that interesting detail, it wouldn't be hard to reproduce the results with four carbon resistors -- no need for nanotubes ;-) There still seem to be references to that article floating around the Web. Not sure if I should interested or troubled... Madhu 20:47, 8 August 2005 (UTC)
5 resistors, right?
          o
          |
          Z
          |
o--V^V^---*---V^V^V---*---V^V^V^---o
                      |
                      Z
                      |
                      o

- Omegatron 20:59, August 8, 2005 (UTC)

I was thinking of something like a bridge, but you might be able to simplify your circuit above to only three resistors:
          o
          |
          |
o--V^V^---*---V^V^V---*---V^V^V^---o
                      |
                      |
                      o

It might not be exactly the same as the Chung circuit, but I'm guessing based on Heron's comments. Madhu 14:33, 9 August 2005 (UTC)

By the way, I completely disagree with this being removed from the article. "Mercy" should have nothing to do with it. We certainly wouldn't be mercifully censorial if it was originally from the free-energy crazies. We shouldn't be any different for this. Besides, this "mistake" has been swallowed up by those crazies and needs to be debunked.
"Now there's one for the environmental activists, if they can really get their act together. Why not swing all that power and clout they possess into action, demanding to know what has happened to Chung's negative resistor? After all, such a unit can easily be developed into systems that will power the world, once the control of the basic effect is worked out — which in this case has already been done by Chung and her team. If the Environmental Community really wishes to do something dramatic to initiate what could be a rapid solution to the hydrocarbon wastes pollution of the planet, this is their big chance."

And here's some images from the paper:

I reluctantly agree with you, Omegatron. When I originally deleted the Chung material, I didn't know that the fantasists had already latched on to it. I thought I was just decluttering Wikipedia of a piece of embarrassingly bad research. Do you agree that, in her paper, Chung displays a lack of clue about circuit theory and the physics of conduction? If, sadly, the idea has got the free energy people all excited, then I suppose we do have a duty to debunk it. --Heron 15:49, 8 July 2006 (UTC)
I'm confused as to what she's actually claiming. The paper explicitly says that it's an "apparent" negative resistance, and isn't breaking any laws, but why call it a "resistance"? Intentionally being misleading for attention? Other news articles say that she is "searching for the mystery energy source". I wonder which came first.
I think we would have a duty to debunk it even if it were only reported by academia and ignored by the crazies. A degree is no excuse for bad science.  :-) The whole point of the academic scientific establishment is to attack each other's articles and research trying to disprove them, until only the Truth remains.
Also, there is nothing I hate more than trigger-happy overblown press releases of legitimate research, which appears to be a major culprit here, as well. — Omegatron 16:48, 8 July 2006 (UTC)
I can tell you where the problem started. On page 1, she directly claims to have done the impossible. First she says "True negative resistance in the former sense [absolute NR] is not possible". Then, in the next sentence, she says "apparent negative resistance in the former sense is reported here". I would say that she is claiming to have broken the laws of thermodynamics. --Heron 19:31, 8 July 2006 (UTC)
But she's making a distinction between "true" and "apparent" negative resistance. — Omegatron 21:20, 8 July 2006 (UTC)
She's making a specious distinction, since her definitions of the two terms are identical. Compare and contrast (from paras 2 and 3 of the Introduction):
"Negative resistance means that ... the current–voltage characteristic is a straight line of negative slope through the origin." (This is what she describes a few lines later as "true negative resistance in the former sense".)
"we report an apparent negative resistance phenomenon in which the entire current–voltage characteristic is a straight line of negative slope through the origin."
What's the difference? (Oh, and she is wrong about it needing to be a straight line.) --Heron 18:41, 9 July 2006 (UTC)
I guess I'm just giving her the benefit of the doubt and assuming that "apparent" means "measured at two different points". But it's misleading, whether she intended it to be or not. — Omegatron 21:53, 13 July 2006 (UTC)
Also, they were just carbon fibers, not nanotubes. — Omegatron 21:57, 13 July 2006 (UTC)

Deborah Chung s 'absolute negative resistance'

I propose removing this content as it is recent research, not relevant, not proven, and probably incorrect or at least misleading. Comments?--Light current 14:27, 1 August 2006 (UTC)

Um, no. We just added the section for good reasons. The discussion we had about adding it is right above you. Did you read it? — Omegatron 15:34, 1 August 2006 (UTC)

Shouldnt this effect be called negative transresistance any way as the experimental device is simple 2 port network? 8-?--Light current 14:57, 1 August 2006 (UTC)

I was thinking of that just now, but I don't think we should include it in the article, since the word is never used in the paper and it's not an active device. As mentioned above, her measurement probably isn't even meaningful, and the experiment and its results are dubious. Citing it as an example of "transresistance" would imply more credibility than it deserves, in other words. — Omegatron 15:34, 1 August 2006 (UTC)

No, sorry I havent been following the argument. Im presenting a fresh, unsullied view. By your latter comments 'O', it seems to me that you are voting for deletion of this material also. Am I correct? If the material is to remain on WP, its proper place is on the transconductance page. Yes? Also when you say its not an 'active' device, in what way would you say it differs from one? --Light current 18:31, 1 August 2006 (UTC)

it seems to me that you are voting for deletion of this material also. Am I correct?
Absolutely not. I'm the one who added it. It was reported in the press as an instance of true, absolute "negative resistance" (with no internal source of energy, which defies the laws of physics). We've added this section to explain what was actually going on (she was measuring current at one point and voltage at another point and calling it a "resistance"). It was then reported in the press that she had discovered a room temperature superconductor (by the University no less!), or reported by cranks as a perpetual energy source (a "true negative resistance"). It is neither. We're not even sure what it's supposed to be, if anything, but we're explaining that it isn't a "true negative resistance". Please read the above discussion. — Omegatron 20:26, 1 August 2006 (UTC)

Well OK 'O' but nevertheless I think this stuff does not really belong on this page. The furore over this wild claim has surely died down now and we should present a stable, long term view on science & engineering subjects. Should we not?--Light current 20:34, 1 August 2006 (UTC)

If someone says "negative resistance? hmmm... i remember hearing about someone who made a real negative resistance a few years ago. i wonder what happened to that. maybe the big oil conspiracy covered it up. let me search wikipedia", they should find something about it. Since this is the article about negative resistance, I'd say it belongs here. If you insist, (and others agree), we can move it to somewhere else and merely link to it from here, but I don't think it deserves its own article. — Omegatron 13:21, 2 August 2006 (UTC)

I agree it doesnt deserve its own article. As I said before, since its a transresistance phenomenon it should go in the transconductance article. A link to the transconductance page should be put at the bottom of the negative resistance page--Light current 15:24, 2 August 2006 (UTC)

  • No one ever calls it a transconductance or transresistance. You might think that's what it is, but we can't publish your personal speculation.
  • Everywhere it's mentioned it's referred to as "negative resistance". By the cranks, by the newspapers, and by the original researcher.
  • I don't think it's a transconductance phenomenon, anyway. It's applying a current to a resistor network and measuring a voltage across another resistor network. It's not even a meaningful measurement from what we can tell. — Omegatron 16:24, 2 August 2006 (UTC)

You say 'No one ever calls it a transconductance or transresistance.' but negative transresistance is exacatly what she describes as measuring. Its a 2 port network!--Light current 18:05, 2 August 2006 (UTC)

If it's a two-port device (which it looks like to me), it belongs somewhere else, IMHO. Everything else on this page refers to a one-port device. I'm not exactly sure where this material should go. I haven't read the paper in great detail, but based on the experimental setup, a multimeter by itself won't tell you if you're dealing with a resistance or a current source. Either way, I am inclined to agree with Light current and recommend moving/removing the material. Madhu 19:33, 1 August 2006 (UTC)
Google search for "negative resistance". The eighth result is about Chung. The seventh through ninth are crackpottery related to Chung's results. There's no better place for this topic. — Omegatron 16:45, 2 August 2006 (UTC)
Retitled this to '..transresistance' as that is what is being described

--Light current 18:29, 15 September 2006 (UTC)

  1. She called it "negative resistance". She didn't use the word transresistance. Calling it that is original research.
  2. Besides, it's not really transresistance anyway; it's measuring four different points of a resistor network. — Omegatron 19:19, 15 September 2006 (UTC)

Two different ideas?

It seems that most of this article is about negative differential resistance, but the Negative resistance circuits section is about actual negative resistances (with a source inside them). Should we split into two articles? Move this article to Negative differential resistance? - Omegatron 23:52, August 4, 2005 (UTC)

"Many circuit topologies are capable of producing negative resistance."

Such a circuit always has a source in it, right? - Omegatron 21:46, August 5, 2005 (UTC)
Right. --Heron 22:14, 5 August 2005 (UTC)

Kron

While debunking the Chung experiment, I noticed another bad science reference to Kron and his negative resistors, so I had to fix that as well. It's obvious from this paper of his that he was talking about perfectly conventional circuits. --Heron 21:28, 5 August 2005 (UTC)

Stop confusing people!!

Whoever made up this page is a @#*^&, stop confusing people if you are not sure! I am tired of marking students' books full of crap.

Negative resistance is an amplifier, it is the working principle of a laser for example. Any amplifier of any form can be consider as negative resistor.

Notice the two references, one is apparent negative resistance, while another is negative differential resistance, i.e. NOT negative resistance.

Negative differential resistance is common in non-linear systems. In electronic it is describe as non-ohmic device. In the case of Neon lamp (where i found this page), it is a run away positive feedback effect.


The term "Negative resistance" should ONLY be use to describe amplifier (i.e. the circuit part of this page). Where the rest of the page should go under the title of "Negative differential resistance"

By "amplifier", don't you just mean "source"? — Omegatron 18:43, 11 November 2005 (UTC)
No, I don't think so... however, it's not exactly an ordinary amplifier, either. Dpbsmith (talk) 18:55, 11 November 2005 (UTC)

To "137.205.164.190:"

My longstanding impression is that "negative resistance" is a very commonly used term for negative differential resistance. I appreciate the point you're trying to make ("negative resistance" = through the origin, "negative differential resistance" = negative slope somewhere not passing through the origin).

However, the issue here is one of word usage. If you're sure that "negative resistance" isn't, hasn't, and shouldn't be used to cover both concepts, would you cite a reliable source for that—say, an electronics dictionary or recent textbook? I, for one, am not ready to update the article just on the say-so of someone who has not even created an account. Dpbsmith (talk) 18:55, 11 November 2005 (UTC)

Hmmm....

http://www.hobbyprojects.com/dictionary/n.html ... "negative resistance: A resistance such that when the current through it increases the voltage drop across the resistance decreases."

Secrets of RF Circuit Design: "The negative resistance phenomena, also called negative differential resistance..."

Practical Rf Circuit Design for Modern Wireless Systems: Active Circuits and Systems by Rowan Gilmore, Les Besser - Technology - 2003: "Negative resistance refers to a component or a circuit where an incremental increase of the applied voltage leads to a decrease of current..."

Basic Electronics by Bureau Of Naval Person U S Navy - Technology - 1973 "negative resistance of the tunnel diode..."

I think you are wrong, or overly prescriptive. "Negative resistance" is, in fact, the common term, and "negative differential resistance" is an alternative term that can also be used that some people prefer as being clearer. Dpbsmith (talk) 19:07, 11 November 2005 (UTC)

I agree that using the term "negative resistance" to mean "negative differential resistance" is terribly misleading.
I think we should be "overly prescriptive" in this article, and only leave it as a note that the term can be used for either meaning. (And I am not the anon.) — Omegatron 19:50, 11 November 2005 (UTC)
Of course not... your style is much calmer and dispassionate. I just asked a colleague, who took out his copy of Horowitz and Hill, and they give an example using a tunnel diode in which they refer to it simply as "negative resistance." I'm thinking that negative "differential" resistance is a fairly common characteristic of passive circuit elements. On the other hand, "true" through-the-origin negative resistance only occurs in active circuits, rarely in a pure form, and is not a customary building block in circuit designs.
Someone designing a circuit might well say "I'll use an operational amplifier here," and buy one off the shelf. But you wouldn't say, "Oh, I think I'll use a negative resistor in here," and buy a little modular two-terminal device marked "-10,000 ohms" containing a little lithium battery inside. Or anything like that. And I'm thinking that ("true") negative resistance is something that happens to occur in certain circuit designs, not a common design element, so it's relatively rarely talked about. So, negative differential resistance is common, "true" negative resistance is rare, and the tendency is to use a short, convenient term for the commonly-talked-about thing.
Anyway, I've shown a recent citation that includes the sentence "Negative resistance refers to a component or a circuit where an incremental increase of the applied voltage leads to a decrease of current." Someone show me one that says that's wrong.
I don't think we should be overly prescriptive unless we're sure that the use of the phrase "negative resistance" for "negative differential resistance" is generally deprecated as of 2005.
I'm perfectly happy to have the article set an example by using "negative differential resistance" throughout, where applicable, because it's perfectly clear and unambiguous. I'm not going to waltz through and strike out the word "differential" or anything like that. But at the moment I am not happy with saying "negative resistance" is incorrect usage. I can easily be convinced otherwise, if someone will bother to show me something convincing. Dpbsmith (talk) 20:17, 11 November 2005 (UTC)
I'm perfectly happy to have the article set an example by using "negative differential resistance" throughout, where applicable, because it's perfectly clear and unambiguous.
That's exactly what I meant.  :-)
Especially because we talk about both in this article, and you probably wouldn't see both concepts in the same place otherwise, so it's ok to be loose with terminology in those contexts. — Omegatron 20:28, 11 November 2005 (UTC)


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