Talk:Negative resistance

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Cosmetic and other edits[edit]

I support User:Spinningspark's revert of User:A876's extensive changes. I don't think any editor should have to go through and manually fix such an extensive change (almost 10K characters). It is enough that some portion of the edit have errors in it. For example, XML requires that attributes be surrounded by quotation marks, so every edit that changed <ref name="foo"> to <ref name=foo> is a poor edit even though such edits work on most XML parsers. We don't assign tasks to other editors; we are volunteers here. Spinningspark need not save edits that fix some subject-verb disagreements (transistor/transistors), some reasonable WL collapses, and appropriate hyphenation. I also find it troublesome that one would defend cosmetic edits ("revert-all WASTES work. restoring ref-errors IS harm. "cosmetic" is NO harm, encourages editors. "potential harm" ≠ harm. there is no "I" in Wikipedia. byp red reveals common target article."). Furthermore, style-only edits should not be done: e.g., changing [[Gas discharge|discharge through gases]] to [[gas discharge|discharge through gases]] is pointless (and why did Hartley go the other way?). Bypassing redirects can violate WP:NOTBROKEN. I think the extensive edit had some reasonable changes in it, but it was presented as an all or nothing affair. Glrx (talk) 23:18, 5 January 2017 (UTC)

Reaction:
  1. "I support Spinningspark's revert ..." (citing Spinningspark's second revert). I find this unsolicited tag-team, ahead even of Spinningspark's comments, scary.
  2. "I don't think any editor should have to go through and manually fix such an extensive change ....." I don't either, but almost nothing needed fixing. Spinningspark's only real objection was my adding unsourced material, which he did not even mention. All Spinningspark had to do was remove the unsourced material and summarize "Sorry, can't keep unsourced material in a good article." (though sourcing it would have been nicer).
  3. "For example, XML requires that attributes be surrounded by quotation marks ..." What possible relevance could that have here? Wikipedia markup is not XML. "Quotation marks are optional if the only characters used are letters A–Z, a–z, digits 0–9, and the symbols ! $ % & ( ) * , - . : ; < @ [ ] ^ _ ` { | }" (See WP:NAMEDREFS.) "... every edit that changed <ref name="foo"> to <ref name=foo> is a poor edit ..." No, it isn't. "... even though such edits work ..." So what is your problem?
  4. "Spinningspark need not [preserve] edits that fix ..." Well, if they "fix", that sounds like a reason to leave them alone.
  5. You quoted my edit summary, but not Spinningspark's summary that I reacted to. I find that lawyering. Spinningspark said "Reverted good faith edits by A876: Most of that edit is purely cosmetic, but some is potentially harmful. Some of the redirects should not be bypassed. There is no good reason for removing quotes from ref names. Sorry, I am not going to p..." I find that summary incorrect and autocratic. I replied honestly (in my edit summary) when I put the same edits back in, that no actual reason was given for reversion: "revert-all WASTES work." (Would you disagree?) "restoring referrors IS harm." (Would you disagree?) "'cosmetic' is NO harm, encourages editors." (Would you disagree? Undoing cosmetic is an even bigger waste: I didn't break anything; pointy.) "potential harm' ≠ harm." (damn right. I didn't break anything.) "there is no 'I' in Wikipedia." (Reacting to the incomplete "Sorry, I am not going to p...". Does someone sit above others?) "byp red reveals common target article." (In one case.) Also you did not quote the summary of Spinningspark's second revert of the same edit (again without the real explanation, unsourced material): "Reverted good faith edits by A876 (talk): I object to this edit, please follow WP:BRD and take it to talk." (there's that "I" again.) (the "R" in WP:BRD is not a prescription.)
  6. "Furthermore, style-only edits should not be done: ..." So? It was not a style-only edit, though there was [much] incidental clean-up of inconsistency. If style cleanup is not done it will either remain wanting, or else be done later anyway (sooner being better). Whether cleanup is annoying or hard to excuse, unnecessarily putting back cruft is atrocious.
  7. "e.g., changing [Gas discharge|discharge through gases] to [gas discharge|discharge through gases] is pointless..." No, it isn't. Piped links are supposed to match the casing of their context, for readability while editing the markup (for those who still edit markup). When [Gas...] is neither a proper noun nor beginning a sentence, is should be [gas...]. If someone did not do it the sensible way, adjusting it for the better is not pointless, it is constructive, and therefore not wrong.
  8. "(and why did Hartley go the other way?)" Why, because I'm an idiot and a hypocrite, of course. Seriously, you couldn't figure it out? Are you trying that hard to hang me? I changed the first "Hartley" from "hartley" in this: (approx)"how feedback oscillators such as [Hartley oscillator|Hartley] or [Colpitts oscillator]s work". Same principle, match the casing that it would have in context. Hartley is proper noun that is always capitalized. If you would make me wrong for fixing that, then I suppose a link like [richard Nixon] would be to your liking if not preference.
  9. "Bypassing redirects can violate WP:NOTBROKEN." Yes, maybe it can. Now what? I try to be sensible about it. Redirects can be distracting on the target page. Very bad piped links are distracting too. See WP:EASTEREGG. A link like [FBI] works with redirect, but a piped link like [Federal Bureau of Investigation|FBI] is better because the user can see on hovering where the link will go (try it: FBI), rather than have to follow it just to get the expansion of the acronym.
  10. "I think the extensive edit had some reasonable changes in it" (thanks) "but it was presented as an all-or-nothing affair." Yes I kind-of do that. If formatting and style were better regarded and standardized, a robot could handle them before or after every edit. But they aren't. Formatting and style are nice to have, but editing only formatting and style is already deemed wasteful, and I agree. So I try to roll in formatting and style edits whenever I have "real" edits; otherwise, tell me, how will they ever get done? This time I took a chance: I did lots of formatting and style, some wikignomish small edits, and hardly any "substantial" edits, and (oops) an unsourced addition. To an article that is possibly better-watched, this "good article" (a medal which seems unmerited, given that it overlooks the most obvious and intuitive application of negative resistance, cancelling out positive resistance of a power cable or motor winding).
  11. It's hard to imagine devoting such time and effort to tearing down an editor, lawyerishly objecting to petty disagreement to the point of not even getting around to stating the legitimate objection. I find most of the edit summaries and the comments here demoralizing and bitey. I am appalled. -A876 (talk) 01:56, 19 February 2017 (UTC)
Just for the record, here are some more things I found objectionable. I am baffled why this editor wants to decapitalize piped links. Bypassing redirects is not always a good thing. For instance Electrical resistance may actually become a standalone article one day (as it once was) so its best to leave links that actually refer to resistance pointing to the redirect. Same goes for conductance. I personally don't especially have a problem with removing whitespace from the ref templates, but presumably the editors who put it in thought it made the edit window more readable. It is just not on for editors that are not primarily content creators to impose a different way of working. That just makes life difficult for the content creators if it is not reverted. That applies to the quotes on ref ids as well. Either the editors have to now change to the new way, or if they don't they risk being criticised for inconsistent formatting at article reviews. If A876 was going to do some major work on the article and worked in a different way there might be a case for a change, but that is not happening here. The only thing of substance added, as far as I could find was sentence on motor speed control. And that was uncited, so if for nothing else, I reverted for adding uncited material. That puts A876 in breach of WP:V, a major policy, for putting it back without providing a ref. SpinningSpark 23:41, 5 January 2017 (UTC)
Reaction:
  1. "I am baffled why this editor wants to decapitalize piped links." (Again with the "I".) Does acceptability of edits depend on whether you understand why? Links work capitalized or not. Why? That allows article names in normal links to take the case that they would have in context, without needing piped links just to handle capitalization. Trivial example: "[Junk] is a form of [junk]." Both links go directly to the article Junk. The same feature allows article names in piped links to take the case that they would have in context, or the opposite case if someone chooses or defaults. But why is using the contextual case better than the opposite case? Because it makes better reading than a CamelCase sentence in the markup. Trivial example: "[Junk (scrap)|Junk] is a form of [junk (scrap)|junk]." That is the preferred form. (Even if I can't re-find the guideline that recommended it.) Naturally, the contrary form works just as fabulously: "[junk (scrap)|Junk] is a form of [Junk (scrap)|junk]." Would you really prefer that? Would you defend that form? Would you get upset if someone adjusted it? Would you put down someone who corrected it? Beyond that, I have to ask, were you really "baffled why this editor wants to decapitalize piped links"? Besides looking at diffs, you must surely have edited markup, but you really couldn't figure out why I would make such a change? Then I hope this was informative.
  2. "Electrical resistance may actually become a standalone article one day (as it once was)..." Probably never, but point taken. [[[Elastance]] (inverse of capacitance) and admittance (inverse of impedance) still have articles. It was a little overreaching, but it was in reaction to "[Electrical conductance|Conductance] is the reciprocal of [electrical resistance|resistance]" - I found it annoying that both links go to [Electrical resistance and conductance] without warning.
  3. "I personally don't especially have a problem with removing whitespace from the ref templates, but presumably the editors who put it in thought it made the edit window more readable." If I come along and I'm smarter than all the other editors, why, I'll indent everything TWO spaces instead of one. That way, if someone does search-and-replace for two consecutive spaces (pointless noise that usually only affects paragraphs), now they get a thousand "false" hits. That's progress? No. More like sabotage. It has to go. Like ridiculous content, ridiculous formatting is up for editing. "If you don't want your writing to be edited mercilessly and redistributed at will, then don't submit it."
  4. "It is just not on for editors that are not primarily content creators to impose a different way of working." Oh, now I get it. There are classes of editors. (Not in any official policies, but I should have suspected.) I was not "impos[ing] a different way of working", I was opposing an unnecessary new way of working, one that can't be found if searching a hundred other articles. A way that wouldn't tragically be possible if the markup had complete standards and/or was self-correcting to prevent all the cruft-puffers who think their idea of breaking and tabbing and indenting is so much smarter than what works everywhere else, for everyone else. "That just makes life difficult for the content creators if it is not reverted." (Again with my scabby stupidity impairing the "real" editors.) No, it deters them from bad habits that should not spread. Let them work on normal pages, before they go indenting and tabifying and inserting random spaces into every paragraph of every article.
  5. "That applies to the quotes on ref ids as well. Either the editors have to now change to the new way, or if they don't they risk being criticised for inconsistent formatting at article reviews." Don't accuse me of making a "new way". I was pulling toward the old way. (Has any editor been "criticised for inconsistent formatting"?) (Is there such a thing as an "article review"? A link might be deserved.)
  6. "if for nothing else, I reverted for adding uncited material" And there it finally is. After two reverts, at the end of the talk-page lecture, you finally give a valid reason for editing. I'm so glad you got round to it. You could have saved a lot of effort by putting it in the first edit summary, instead of a rant about things that don't matter ("cosmetic", "potentially harmful", "no good reason", and "Sorry, I am not going to p..."). Very, very discouraging. -A876 (talk) 01:56, 19 February 2017 (UTC)
@A876: Thank you very much for removing [1] the illegal links in citation templates; that was my screwup (an error I also committed on numerous other pages). As for the other edits, although your motives were good, I support Spinningspark's and Glrx's remarks above. --ChetvornoTALK 01:43, 6 January 2017 (UTC)
I'm okay with parts of what they did and said, but I could never provide drive-by "support" for such foot-wiping. -A876 (talk) 01:56, 19 February 2017 (UTC)
Being reverted is standard procedure at Wikipedia—it should not evoke walls of text, and reactions should not include claims of tag teaming or foot wiping. Further responses are not needed. Johnuniq (talk) 02:54, 19 February 2017 (UTC)

The Deborah Chung paper[edit]

@Glrx: What was your objection to including the example of the Chung paper? I was trying to show the reaction of the electrical engineering profession to a report of negative absolute resistance. I thought it was a good example.

A negative absolute resistance (as opposed to a negative differential resistance) produces electric power, so negative absolute resistance in a passive material (her carbon fibers) is equivalent to "perpetual motion"; energy from nothing. In the news sources I gave: [2], [3] the scientific community quite properly reacted to Chung's paper by making it clear that that is impossible. Primary research often is in error; the conclusion of mainstream scientists was that her observation of negative resistance must have been due either to some small "active" process in the material; a contact potential or electrochemical reaction which produced a potential difference, or a defective measurement technique. As far as I can tell, the cause of her negative resistance measurement hasn't been resolved yet, but that doesn't mean anyone believes carbon fibers can produce energy from nothing. The point of the example is the reaction of the scientific community: negative absolute resistance in passive materials violates the laws of thermodynamics. --ChetvornoTALK 02:52, 28 March 2017 (UTC)

I'm fine with no perpetual motion references, but an encyclopedia isn't interested in small details. There's no point in calling attention to one paper. The rebuttal refs are not strong (judgment from an abstract rather than the paper). Your comments about no resolution make the issue even cloudier. There's a touch of WP:SYN. Glrx (talk) 03:28, 28 March 2017 (UTC)
I agree with Glrx—articles should avoid news-of-the-day, particularly when it enters WP:REDFLAG territory. This article is about what negative resistance has meant for over fifty years, not breakthroughs that might be valid. Johnuniq (talk) 03:47, 28 March 2017 (UTC)
That was the whole point of the example, Johnuniq. The content Glrx removed said:
"For example, in 1998 materials scientist Deborah Chung reported finding apparent negative static resistance in carbon fiber composites. Her paper was met with disbelief from scientists.[citations] Her observations have not been repeated by any reputable lab."
Negative resistance means a violation of the 1st or 2nd law of thermodynamics. That's not "news-of-the-day", it's been accepted a lot longer than 50 years, since 1892. So reputable scientists rejected Chung's claim - exceptional claims require exceptional proof. The text nowhere says the claim is valid, where is the WP:REDFLAG? The text supports everything you said above.
Glrx, the violation of the laws of thermodynamics is not a "small detail". That's why Chung's obscure material science paper was the subject of a Los Angeles Times article and an editorial in the journal of the Electric Power Research Institute. The refs quote plenty of "rebuttals" from scientists: Cetin Cetinkaya:"Physically, that's not possible." Steve Kivelson: "It's impossible." Brendt Fultz: "...it's violating one of the two laws of thermodynamics." If by "rebuttals" you mean experimental evidence contradicting Chung, I suspect this case is pretty typical of reported 2nd Law violations. It's been 20 years and Chung's data has not been repeated, AFAIK. For this "exceptional claim" the burden is on Chung's supporters to provide more evidence than a single experiment, before the scientific community takes them seriously. They haven't been able to do that, so it's pretty clear that her observation was a fluke, like many, many "unrepeatable results" before it.
And where is the WP:SYN in the text I added? --ChetvornoTALK 11:02, 28 March 2017 (UTC)
I have to agree with others that this is a bit out of place. It's a bit like introducing perpetual motion into the engine article only to then shoot it down (although I'm not suggesting that Chung is a fringe crackpot). It's not as if more sources were needed to support the article text. There are already more than enough, too many it could be argued. It's also somewat odd to bury the discussion in the references. If we are going to discuss it here it should be in visible text in the body of the article. But I really think Chung's page is a more appropriate place, or perhaps the perpetual motion page. SpinningSpark 13:05, 28 March 2017 (UTC)
Actually the sources for this section are particularly weak, which is why I included so many. Spinningspark, I certainly disagree with your argument that a report of negative resistance is "out of place" in the Negative resistance article. The reason I "buried" the discussion in the references is the same reason that you want it omitted altogether. The scientific community didn't believe Chung's claim, and her observations haven't been repeated. Discussing it in the article would give it WP:UNDUE WEIGHT; give the erroneous impression it was considered seriously; it would be WP:REDFLAG, as Johnuniq said. I thought if it was presented correctly, as a footnote, readers would see it as it is: a single irreproducible result contradicting a 400 year old law of physics, and so not to be given much weight.
However, I thought about your (collective) objections, and I guess you all have a point. Including the Chung claim in the article at all, without a clear refutation, is inevitably going to give some general readers the wrong idea, be UNDUE WEIGHT and REDFLAG. I accept Glrx's revert. --ChetvornoTALK 01:45, 29 March 2017 (UTC)

Opening paragraphs[edit]

The opening paragraphs of this article seem a little confusing to me. It says that as voltage is increased the current decreases, but that seems a little backward. How do you increase voltage when resistance is falling? That seems like trying to increase the pressure of a waterfall by spraying a garden hose into it. As I understand it (and please correct me if I'm wrong) as current is increased, both the voltage and resistance decrease.

When most people talk about voltage, they're talking about open-circuit voltage (OCV), which is when voltage is at its highest. When the circuit is closed, there is a voltage drop as amperage increases. Resistance is what limits this voltage drop and, per Ohm's law, the accompanying increase in current. In a normal resistor, heat is generated which actually increases its resistance. A hydraulic analogy is found in a simple water faucet. When the faucet is closed, pressure in the line is highest. When fully open, the pressure is lowest and flow is highest. Opening the faucet a little bit increases its resistance to flow, so the pressure drop is smaller and so is the flow. (Keep in mind that "open" and "closed" mean exactly the opposite with electricity as they do in hydraulics.)

For negative resistance, when the circuit is closed, the voltage drops accordingly, and the amperage increases. The difference is that as the plasma heats up, the resistance begins dropping along with the voltage, thus the current runs away like a freight train. (A hydraulic analogy is that as soon as you crack the faucet, it blows off and water flows just as fast as the pipe will allow, and pressure drops to almost nothing.) Zaereth (talk) 20:07, 30 March 2017 (UTC)

This is a pretty complicated subject, and hydraulic analogies are not going to get you very far. I don't think there is any effect in hydraulics which is analogous to negative resistance (a decrease in flow rate through a hydraulic system with an increase in the pressure across it?). I'll try to answer your questions
  • "When the circuit is closed, there is a voltage drop as amperage increases." This is caused by source resistance, a positive resistance. Any source of power has internal resistance resulting in a drop below the open circuit voltage when current is drawn.
  • "As I understand it (and please correct me if I'm wrong) as current is increased, both the voltage and resistance decrease." You're right. Keep in mind there are two kinds of resistance; the "absolute" or "static" resistance, V/I which is what you are talking about, and the differential resistance ΔV/ΔI. Anything can happen to the differential resistance; it can increase, stay the same, or decrease.
I-V curve of gas discharge. Note that the vertical current scale is exponential
The fluorescent tube is not the best example to introduce negative resistance, because due to hysteresis the current through it doesn't change continuously as a function of voltage, but in "jumps". I just added the picture because it is the most common device with negative resistance readers will be familiar with.
A gas discharge tube like a fluorescent light has a type of negative resistance called "current controlled" or "S type" (see Negative resistance#Types). The graph (right) shows its current-voltage curve; the voltage across the tube at any given current. The negative resistance region is between D and G. When a voltage source (the power line) is connected across it that is greater than its breakdown voltage D (about 700 V on this graph), this causes an effect called hysteresis. The current becomes unstable and increases exponentially, only limited by the external circuit. This is caused by a "chain reaction" of ionization in the tube. You could say the tube's absolute resistance "drops", but keep in mind the tube doesn't have a "resistance" at all currents because the current changes in jumps. In this regime the tube cannot operate stably at points on the curve where the differential resistance is negative (sloping down to the right, such as between E and F or I and J)(see Negative resistance#Stability conditions), the current can only be stable at points of positive differential resistance (A, B, C, D, G, H, J, K).
If the external circuit has sufficient resistance or other current-limiting device (such as a ballast) the current can stabilize at a positive resistance point higher on the curve (around G and H). At this point the current will be higher but the voltage across the tube will be lower, reduced by the voltage drop across the current limiter, so the tube's absolute resistance is lower. The tube will have a glow discharge and emit light. This is what happens in a working fluorescent light. If the external circuit has insufficient resistance, the current will continue increasing to the regions J and K where the discharge becomes an electric arc which releases a great deal of heat, causing failure of the tube. --ChetvornoTALK 10:29, 31 March 2017 (UTC)
Ok, I see what you mean. I was under the impression that a fluorescent lamp operates in the arc regime, but could be wrong. None of the glow discharge lamps I've built ever needed a ballast to control the current; they could be connected directly to the transformer or line voltage, like a neon sign. The ballast seems to be necessary only when I crossed into the arc regime, where the current runs away on its own. (The exception of course is a flashtube.) Once this happens, no increase in voltage is going to extinguish the arc (which is what I was getting from the opening paragraphs.) Zaereth (talk) 17:17, 31 March 2017 (UTC)
You make neon lights? Cool. I know the term "arc light" is used for some gas discharge tubes, but I'm pretty sure fluorescent lamps and neon lights operate in the "glow discharge" regime. I don't know exactly how the current is limited in a neon tube light. I believe I read somewhere that the neon sign transformer is designed with large leakage inductance so it acts as a ballast, limiting the current so it doesn't run away? --ChetvornoTALK 18:37, 31 March 2017 (UTC)
A photo of of one of my few surviving argon-flashtubes. For this one I used Viton O-rings to seal the electrodes initially, and then an epoxy to permaneantly seal them after bombardment.
I've made some simple ones in my younger days. Mostly I was trying to figure out how to make flashtubes that wouldn't explode or lose pressure over time. (Made well over 400, of which only four survive to this day. It really wasn't until I began talking to experts, like Harold Edgerton or Don Klipstein, and even had one owner of a company give me a bunch that he was going to throw away, that I finally succeeded in making my first operational laser.) I've got a nice, big neon-sign transformer that's perfect for bombarding (removing oxygen that adheres to the glass) small flashtubes and arc lamps. The transformers needed to bombard a full-size neon sign are monstrous. (Typically about the size of a 55 gallon drum. Way out of my price range.)
Nearly every book I've seen on fluorescents seem to call the discharge an arc. Of course, that doesn't mean they are always correct, so now I'm curious to dig deeper. Neon signs definitely operate as glow discharges, though. The small neons (like you often see in an extension cord to indicate it's plugged in) are connected directly to the line. Zaereth (talk) 19:06, 31 March 2017 (UTC)
I talked to a friend of mine who knows more about this than I, and he turned me on to this source, which gives wonderfully detailed explanations of the various discharges. (Cleared up a few of my misconceptions.) Fluorescent tubes are definitely low-pressure arc lamps, because they require the thermionic emission of electrons from the cathode to support their operation. The exception to this are cold-cathode fluorescents (often used in computer backlighting), which are are basically fluorescent tubes operated like a neon light. Neon signs also fall under the category of cold-cathode lamps. When a fluorescent is perpetually lit, the main process of wear becomes adsorption of the mercury onto the glass, which eventually reduces its pressure enough to move it into the glow-discharge regime, causing it to dim and eventually form visible Faraday cones that move from the ends toward the center. (This may also bee seen during start-up, especially in 8 foot T12s, before the tube heats up and increases in pressure as the mercury vaporizes.) Zaereth (talk) 00:28, 4 April 2017 (UTC)
Say Zaereth, I'm sorry, when I wrote the above comments I forgot that you have a great deal of experience with this stuff in building lasers (guess it was a senior moment). Most of what I wrote is probably not news to you. You met Harold Edgerton? Wow.
Yes, that gas discharge page by Calvert is absolutely great, I ran across it before, that's where I learned what little I know about the subject. It would be good to put some of that stuff into the Glow discharge article, which in my opinion needs a rewrite. BTW, editor Glrx has the most expertise in this area of anyone I know, and he would be the person to ask questions of. --ChetvornoTALK 01:55, 4 April 2017 (UTC)

──────────────────────────────────────────────────────────────────────────────────────────────────── Hmm. This comment is going to take some time.

I'm always in an extended senior moment.

The negative resistance issue is just that at some point on a transfer curve the dV/dI slope becomes negative.

One issue is whether current or voltage (or neither) is controllable. The WP article intro uses voltage as the independent controllable variable, but that is probably the less common one. As the voltage increases across a positive resistance, we expect the current to montonically increase. For a (differential) negative resistance device, increasing the voltage a little bit might cause the current to decrease from its previous value. For each voltage value, we can plot a stable current.

Sometimes, the current is controllable: for each current, there is a specific output voltage. Somewhere in that transfer curve the voltage falls as the current increases. The classic example is a tunnel diode.

If the other variable is driven, then strange, counter-intuitive, things happen. If I increase the voltage across a tunnel diode, the current will slowly increase. At some point, I hit the negative resistance point and the current takes a discontinuous jump to a much higher value. Increasing the voltage when the resistance is falling becomes harder to do.

Now we get into disputed territory.

Many people use a glow discharge lamp as an example of a negative resistance. Chetvorno supplies the plot above, but the plot has problems. It shows a continuous transfer function on the hysteresis path, but most references do not show that. Instead they show a breakdown transition or an unstable region. I think a breakdown is the better explanation because the Townsend discharge to glow discharge involves a reorganization of the charge within the breakdown. During the Townsend discharge, the electric field is evenly distributed. At breakdown, the world changes: most of the field is at the cathode fall and there is a small field in the rest of the tube (positive column). It takes some time for that field to develop. The plot of the discharge tube is a steady state transfer function rather than an instantaneous IV characteristic (like a tunnel diode). The hysteresis is there because once the charge distribution is set up for a glow, it will keep that distribution until the current falls much below the current needed to start the glow in the first place.

In many cases, one can plot a steady-state transfer function with an apparent steady negative resistance. IIRC, Laser tubes are an example: the more DC current run through them, the lower the voltage drop across the tube. Zaerth points out that the gas is heating up, and that means there an additional state change rather than a negative resistance. Consider a negative temperature coefficient thermistor; if I increase the voltage across it, it self heats and becomes a lower resistance. We don't consider that a negative resistance because a steady state DC transfer function could show a negative resistance characteristic.

Similarly, some arc discharges have a thermal explanation. Joule heating at the cathode increases the temperature enough that thermionic emission takes over. The steady state transfer curve shows a negative resistance, but there's an underlying state change.

Yes, Calvert is an excellent source that explains a lot of this material; I stumbled across it a couple years back. User:Glrx/sandbox#Glow character.

BTW, the small neon lamps are not connected directly to the line; there's a limiting resistor. A friend and I were looking a neon night light when he suddenly realized the night light took more power when it was off than when it was on. A photoconductive cell was used to short out the lamp when it was too bright.

Chetvorno, Zaereth knows much more about gas discharges than I do. Years ago, I asked a friend about gas breakdown, and he gave me a fabulous introduction. Most of what I've picked up since then is from some ancient text books and a few research missions to the library. Much of that effort has raised more questions in my mind than they've answered. I've been meaning to read Penning's book, but I haven't gotten around to it. I've also been meaning to measure the dynamic characteristics of an NE2 and see if shielding it can increase turn on time.

I had a lot of fun talking to Doc Edgerton. I got an invite to be on the boat where he was trying out the side scan sonar just before going on his Nessie quest. The monster search was a good excuse to try out some interesting equipment. Driving a piezoelectric sonar transducer got me to understand inductors and impedance matching much better.

PS, say hi to Steve.

Glrx (talk) 04:17, 4 April 2017 (UTC)

Thanks, I'm flattered. The math is my weakness so I have to really try hard to follow along. (Some of the best books on lasers are written in nearly 80% math.) My strength and weakness is that I have to try to understand things from a mechanical perspective. I really envy your ability to read the complicated math equations. I did learn quite a lot from both yours and Chetvorno's explanations. I had always assumed the glow discharges were stable, in the sense that they wouldn't runaway, but it turns out I was mistaken. Checking some books, Chet is correct. The high reactance of the neon transformers provides the current limiting needed, which makes them perfect for He-Ne lasers or small CO2 lasers. Otherwise there needs to be a current-limiting resistor or ballast. However high-powered CO2s require a ballast, or else you need a current limiting resistor about the size of a 1500 watt space-heater. These lasers can't perform as arcs because the temperature increase tends to depopulate the lower energy states, reducing output to nil. Zaereth (talk) 07:40, 4 April 2017 (UTC)

Recent revert[edit]

@Glrx: what is your objection to the clause? Is it just the word "electronics" or the entire addition? --ChetvornoTALK 14:35, 30 April 2017 (UTC)

The entire clause. Many complaints. Let's start with a source for the statement. Glrx (talk) 20:23, 30 April 2017 (UTC)
Most of these are already cited in the "Active resistors" section. Also, as explained in that section, it can be seen from the equation for the input resistance of a positive feedback amplifier that if the loop gain (the regeneration) is greater than one, the input resistance will be a negative number. --ChetvornoTALK 07:53, 1 May 2017 (UTC)
I think the issue is that active resistor is not synonymous with positive feedback. Sufficiently large positive feedback will give rise to negative resistance, but the terms are not sysnonymous. It is not even true that negative reistance iff positive feedback, since low positive feedback gives positive resistance (although it always reduces the pre-existing resistance). I would also question the implication that active resistor implies negative resistance. A resistance generated through negative feedback is still an active circuit to my mind, but the resistance is positive in that case. One can also produce a resistance with an active circuit without any feedback at all. SpinningSpark 12:49, 1 May 2017 (UTC)
@Spinningspark: The sentence Glrx reverted
"In circuit theory these are called "active resistors", but in electronics this property is more often just called regeneration or positive feedback."
does not exactly say active resistance is synonymous with positive feedback. It just says because more specific terms for this property like "active resistance" are not used much in electronics literature yet, this behavior is just lumped under the terms "regeneration" or "positive feedback". Also, since as you say positive feedback (regeneration) always results in a lower resistance than if there were no feedback, in that sense any amount of positive feedback adds "negative resistance" to a circuit. I wouldn't mind the above sentence being edited to make it clearer, but it should not just be deleted. It's important to explain to readers that they're not usually going to find this kind of negative resistance called "negative resistance" or "active resistor" in the literature. --ChetvornoTALK 16:15, 1 May 2017 (UTC)
@Spinningspark: Re "I would also question the implication that active resistor implies negative resistance". I agree. The term "active resistor" has several other meanings in electronics [4], [5] such as a transistor with negative feedback applied to give it high (positive) resistance, used as an active load for another transistor [6], [7]. That should probably be noted in the section.--ChetvornoTALK 16:15, 1 May 2017 (UTC)