Talk:Electrical resistivity and conductivity

Mistaken postulate in Definition section?

Just a quick question. Unless I misunderstand something, under the heading "definition", it seems like the discussion about the definition of resticivity mistakenly reverses the point. Resticivity is defined as R=V/I, which is an intrinsic property of materials, while p=R*A/l specifies, as I read it, the resistance of an OBJECT, which varies with its geometry and is thus determined by its geometry and the intrinsic property, R, of its substance. But the article states the opposite. Or what? I know nothing about the subject, so might just be misreading it. I.e. it says:

"The reason resistivity is defined this way is that it makes resistivity an intrinsic property, unlike resistance.", but the rest of the content indicates that the words have just been swapped by mistake. I will not correct it, since I am no expert, but I urge someone to correct it if it is a mistake.

You say "V/I is an intrinsic property of materials" but that's not true. A long thin copper wire has a different V/I from a short thick copper wire, even though both are copper. --Steve (talk) 12:06, 16 May 2016 (UTC)

Don't think there's anything mistaken here. As Steve stated, V/I or resistance isn't a property of materials. You seem to have mixed the two up. A piece of a substance has a certain resistance but a substance itself has a certain resistivity rho. An analogue that might be familiar to you is mass vs density. Density is defined as mass per unit volume, making it an intrinsic property of a substance itself. Similarly with resistivity, we are looking at resistance per unit length of wire, adjusted for the cross sectional area of the wire. If you measure the resistivity or density of a substance, it will always come out the same regardless of the sample or the size. 67.188.175.172 (talk) 10:56, 9 January 2018 (UTC)James

Dubious phrase

There is a hypothesis that electron pairing in high-temperature superconductors is mediated by short-range spin waves known as paramagnons

This phrase caught my eye because of new term I made redlinked. I did some reading and found this text saying that paramagnons are in fact suppress superconductivity. So, how they can "mediate"? Does somebody have access to the footnoting article to verify what it actually says? Staszek Lem (talk) 20:22, 5 August 2016 (UTC)

There are different kinds of superconducting states. If I am not mistaken, the text you refer to talks about conventional s-wave superconductivity. The high-Tc state is usually assumed to be d-wave, and the shape of the Fermi-surface also plays a role, so that the effect can be different. This is a complicated subject which I do not claim to understand, but I see no contradiction here. The reference in the article [D. Pines (2002)] is also of high quality and supports this claim, although it talks of spin fluctuations instead of paramagnons, but these are more or less synonymous. Jähmefyysikko (talk) 18:48, 26 December 2021 (UTC)

Resistivity of Deionized Water?

Appears to be wrong: low by 100X. The ref is behind a paywall. Can someone with access verify it? The usual value for well-deionized water is 18e7 ohm-cm, not 18e5 71.37.36.149 (talk) 02:50, 6 March 2017 (UTC)

There is another source here, which does indeed give 18 MΩ·cm = 0.18×10⁶ Ωm = 1.8×10⁵ Ωm – the figure given in our article (as well as in purified water). You might have been confused by the choice of units – this article uses Ωm rather than Ω·cm. No such user (talk) 13:22, 6 March 2017 (UTC)

I was just looking at this table and noticed the same. DI water should be 1.8e7. — Preceding unsigned comment added by 67.159.168.22 (talk) 23:26, 3 June 2019 (UTC)

Disregard. I made the last comment, then attempted to update and was successful. — Preceding unsigned comment added by 67.159.168.22 (talk) 23:28, 3 June 2019 (UTC)

I noticed that the resistivity value was still incorrect (1.8e7 Ohm.m) in the table (but conductivity value was correct, hence the table was inconsistent). I have now updated the table to the correct resistivity value of 1.8e5 Ohm.m, which is the same as 18 MOhm.cm. EV1TE (talk) 14:03, 5 November 2019 (UTC)

Conductivity of air versus absolute or relative humidity

It is well known that experiments on static electricity work better under dry than humid conditions. The usual reason given is that humid air conducts electricity better than dry air, but if so does that depend chiefly on relative or absolute humidity? I would guess absolute, since that's what corresponds to the actual ratio of water molecules to air molecules. Another way of asking this question would be to ask, at a given absolute humidity, does the conductivity of air vary with temperature (which would change the relative humidity). I could not find tables of the conductivity or resistivity of air versus humidity in a cursory Web search, so I'm beginning to suspect that the answer may be more complicated, e.g. in addition to an effect on the conductivity of air, humid conditions (especially high relative humidity) may moisten the surfaces of otherwise insulating solid materials, making them more conductive, and thereby hastening the dissipation of charge otherwise than by actual conduction through the air. In any case, since the effect of humidity on conductivity of air is of great interest and practical importance, there should be a section on it, hopefully with a table or graph of reliable values, and/or an explanation of more complicated aspects such as those I conjecture here.CharlesHBennett (talk)

The conductivity of air (or any other gas) depends on a lot of factors. One very dominant factor is the background radiation as this is one of the major sources of free electrons in gases, which is also the dominant component for conductivity. Temperature, pressure, etc. affects free electron life-time and radiation absorption etc. Humidity affects surface resistivity of nearby insulating materials, which affects static electricicty measurements etc. Hence I do not think it is relevant to try and list precise values for conductivity for air or other gases, however some generic value +- 10x or so might be nice just for reference. EV1TE (talk) 14:14, 5 November 2019 (UTC)

de:Elektrische Leitfähigkeit

Why is there one page for two terms?

• Electrical conductivity de:Elektrische Leitfähigkeit
• Electrical resistivity -> de:Spezifischer Widerstand

that causes problems wit the interwiki links. --Manorainjan (talk) 16:24, 20 July 2017 (UTC)

As explained at Wikipedia:Wikipedia is not a dictionary, an article is about a concept or topic, not a word, so it is common for multiple very-closely-related terms to be defined in the same article. In many cases, it is not obvious whether articles should be merged or split, and there are debates / discussions about what to do. But each language's wikipedia is entitled to make its own independent decisions about which articles exist and what their scope is. If you think that the article should be split in two, you can propose that and make arguments for it, but if "German wiki did it differently" is your only argument, I think that's a very weak argument. Maybe this article should stay the same and German wiki should merge them! Or maybe different ways of organizing the information make sense in the different contexts, and problematic interwiki links are just an inevitable problem we'll have to accept. :-D --Steve (talk) 01:39, 21 July 2017 (UTC)

conductivity of graphene

Currently, graphene is listed as the material with the highest overall conductivity. Independent of whether this is correct or not, it is not supported by the cited press release. Actually, one of the scientists involved in the work, states in another news piece: "Other extrinsic sources in today's fairly dirty graphene samples add some extra resistivity to graphene, so the overall resistivity isn't quite as low as copper's at room temperature yet. However, graphene has far fewer electrons than copper, so in graphene the electrical current is carried by only a few electrons moving much faster than the electrons in copper."

In general, I would vote to remove graphene from this list as it is clearly an outlier. Comparing the properties of a (nearly perfect) single sheet of atoms against "real materials" with defects doesn't seem fair. --Leoteo87 (talk) 18:03, 20 November 2017 (UTC)

I agree, the 1e-8Ω·m =1μΩ·cm figure mentioned in the press release is described as a theoretical value of one contribution to resistivity by itself, not an all-things-considered prediction let alone a measurement. I would be happiest if it were deleted altogether, although I'm OK with it being replaced with a measured value.

I prefer deletion to fixing because it's a single-layer material by definition -- if you fill up a 3D volume with it then it stops being "graphene" -- and therefore is most usefully described by a sheet resistance not resistivity. Also, the resistivity varies dramatically with gate / doping (like other semiconductors / semi-metals). --Steve (talk) 22:22, 20 November 2017 (UTC)

Sodium

Hi, I see there is one table with Sodium and Lithium and their resistivity and res - volume products. But the Sodium is not present in the main table. I cannot find the main source for the sodium conductivity either or its dependence on temperature. 81.6.34.246 (talk) 17:55, 14 July 2018 (UTC)

"Conductor cross-section/volume ratio, at same conductance as copper" column

I deleted the rightmost column of the Resistivity density products table with the comment

delete rightmost column, i.e. conductivity vs copper, which is confusingly worded, redundant with the conductivity column, and somewhat off-topic for that section

Then Dqeswn (talk · contribs) put it back in with the comment "restored arbitrarily removed column".

I re-deleted again just now, but anyway I'm happy to discuss. Again, see my comment copied above for why I think it should be deleted. --Steve (talk) 16:48, 31 July 2018 (UTC)

Why does it hurt you to have related information there instead of emptyness? It's a factor that significant when you select better materials for resistivity density. Because as a side affect you get an increase in conductor cross section (so also volume). Besides it's calculated from and is a consequence of the same material properties resistivity density is calculated from. Also: if you don't like the wording, improve it (but I believe I've done so already). Dqeswn (talk) 17:03, 31 July 2018 (UTC)

Well, it hurts, being just arbitrary data that does not bring any new information to the reader. Next thing you know, we can add the value relative to aluminium, water or steel. Relative densities are pretty obvious from the next-to-last column, in the same order of magnitude. No such user (talk) 18:05, 31 July 2018 (UTC)

Emptyness is not always a bad thing. Textishardertoreadifyouleaveouttheemptyspacesbetweenwords, right? The limited resource is not space, but rather readers' time and attention span. A table with five columns is by default slightly easier to read and understand than a table with six columns, simply because there's less text to parse and digest. So that's the price we pay in adding a column. Do we get a benefit commensurate with that price? In this case, I say no.

This is the section on the resistivity × density product, which is relevant for people trying to minimize weight per conductance. So we can have columns saying the name of the material, the resistivity × density in SI units, the resistivity × density in easier-to-parse units, and the resistivity and density that allow readers to understand why the resistivity × density values are what they are. All those columns make sense, and are very valuable for the customers of that particular section, i.e. the people interested in how to minimize weight per conductance. Is it possible that some readers are interested in minimizing volume per conductance rather than weight per conductance? Sure, that's entirely possible. But they shouldn't be reading the resistivity × density section in the first place, they should be up looking at the main resistivity table, the one without density in it.

In reality, if I were personally building a mains electricity transmission line, I would be interested in (1) resistivity, (2) density, (3) price, (4) strength, (5) longevity, (6) availability, (7) lead time, (8) CTE, and dozens of other factors. It's not like adding your proposed column makes the difference between "having all relevant information necessary to build a mains electricity transmission line" and "not having all relevant information". It's just adding one more little bit of information out of the giant pool of relevant information. And the one bit it does add happens to be one that's already on the table! (in an only-slightly-harder-to-read form.) Do you think we should add dozens more columns to the table with all those other factors I mentioned? If not, why not? --Steve (talk) 18:12, 31 July 2018 (UTC)

It shows the fallout (in volume/cross section) from moving from standard copper to materials with better resistivity density. It's very relevant information.Dqeswn (talk) 13:27, 12 August 2018 (UTC)

Too technical

And since the first idea most people have access to is conductivity, rename to electrical conductivity and resistivity. -Inowen (nlfte) 02:57, 1 September 2018 (UTC)

We're all volunteers here. If you want the article to get better, you should try to help! :-D Writing the two words "too technical" and putting on the template is not quite completely useless, but it is very far from being as helpful as you could be. When I look at the article, as an expert, I see room for improvement (as always), but nothing jumps out at me as especially technical, i.e. far beyond what's necessary for talking about a technical topic, or far beyond what's typical for other wikipedia articles of this type. But I wouldn't know, would I? In fact it's almost impossible for an expert like me to create pedagogical material without very specific feedback from people trying to learn. Exactly which parts of which sections are too technical, and why? Did you find jargon-y words, and if so, which words, and can you try to find an easier-to-understand synonym? What exactly were you trying to learn that you couldn't learn, and what is your background? Did you look elsewhere for an explanation you could understand better, and if you found one, what was it?

I don't have a strong opinion about "electrical conductivity and resistivity" vs "electrical resistivity and conductivity". I personally learned about resistivity before conductivity, Inowen says they learned it the other way around, and I don't have any basis for guessing which of those is more common in the world. --Steve (talk) 20:40, 1 September 2018 (UTC)

Impedivity or impeditivity

This article uses a word (impeditivity) in the "Complex resistivity and conductivity" section. The word does not appear to be in use elsewhere (bar one or two links). Impedivity seems to be the term used in the links to academic publications. Wiktionary also has an entry for impedivity [1] and admittivity. Neither appear in mainstream dictionaries, although you can find the word impeditive. Maybe that's why "impeditivity" was used in this article, for the sake of some kind of grammatical consistency. — Preceding unsigned comment added by 2001:BB6:7011:BB58:CC6C:940F:7C15:1528 (talk) 06:47, 15 October 2018 (UTC)

Thanks, I fixed it. It was probably just a simple mistake. --Steve (talk) 12:43, 15 October 2018 (UTC)

"Electrical conductivity or specific conductance is the reciprocal of electrical resistivity," but graphite is the most conductive while silver is the least resistive.

I'm just going to put this out here. If you sort the table by least resistivity you get different results than if you sort by highest conductivity. This conflicts the idea of them being inversely proportional. — Preceding unsigned comment added by 67.82.58.216 (talk) 01:26, 5 November 2018 (UTC)

Fixed ^talk2siNkarma86—Expert Sectioneer of Wikipedia 23:59, 5 November 2018 (UTC)

Inconsistency in values

In the table of resistivities and conductivities, the values for hard rubber and diamond (and possibly others) are inconsistent. Resistivity is the inverse of conductivity, but in both of those there's a factor of ten difference between their stated conductivity and their stated resistivity. Could someone verify which value is correct and fix the table? 104.167.148.149 (talk) 16:04, 5 July 2019 (UTC)

I agree, many values are inconsistent. It would be a quick fix to just open the values in excel and calculate one from the other, the issue is that one does not know which is correct and which is incorrect. Some values also seem to be confused with the older CGS-units Ohm.cm, but this article uses SI-units in Ohm.m. EV1TE (talk) 13:36, 5 November 2019 (UTC)

Actual testing

For your information, many years ago testing the VR on chlorinated paraffin and PVC was a common part of my role. The testing on PVC compounds in the form of a sheet about 4" x 4" was done using mercury. I am sure it's not done like that now! — Preceding unsigned comment added by 86.188.183.86 (talk) 14:51, 6 July 2020 (UTC)

GaAs has huge range for conductivity and resistivity

GaAs has huge range for conductivity and resistivity here (10^11) - presumably between intrinsic and doped, but Si and Ge only give one value so we should/could perhaps note its intrinsic (undoped) conductivity & resistivity ? GaAs says " high resistivity of 10⁷–10⁹ Ω·cm ....[9]" ie 10⁵–10⁷ Ω·m ? - Rod57 (talk) 12:40, 25 October 2021 (UTC)

Glass has wide range for conductivity and resistivity

Can we separate types of glass near the extremes of the 1:10,000 range given ? soda glass ? borosilicate glass ? lead 'crystal' ? - Rod57 (talk) 19:14, 25 October 2021 (UTC)

§ In metals: Distracting Newton's cradle GIF

Is it really necessary? I can't, for one, focus on reading the text with that so entertaining/distracting never-ending GIF. --TwainNeverSaidThat 15:58, 20 March 2022 (UTC)

I was the one who originally added it to the article, but I see (and empathize with) your point. I think it's a useful illustration of a mechanical analogy. Should we perhaps replace it with a proper video, such as the one to the right? No such user (talk) 16:19, 20 March 2022 (UTC)

@No such user: I didn't want the illustration removed, if you were thinking that. Yes, replacing it with a video sounds good. Thank you. --TwainNeverSaidThat 13:25, 21 March 2022 (UTC)

Article issues and classification

The article has a multitude of sourcing issues. The criteria #1 states; The article is suitably referenced, with inline citations. It has reliable sources, and any important or controversial material which is likely to be challenged is cited. #4 states, The article is reasonably well-written. Articles tagged as "needing clarification (October 2021) and "disputed statements" (October 2021) are not indicative of being "well written". Reassess article to C-class. -- Otr500 (talk) 02:49, 1 March 2023 (UTC)

I think we need a section dedicated to materials and their conductance. — Preceding unsigned comment added by Clepenji1150 (talk • contribs) 16:28, 20 March 2023 (UTC)

kappa is never used as a conductivity symbol?

The current version says kappa is used in EE for electrical conductivity. In my 30y career (not in EE but in physics/MSE and working closely with electrical engineers) I never witnessed that. I just googled EE textbooks and out of the 6 I looked at, 4 use the usual sigma and the other two never introduce a symbol for conductivity. On the other hand, kappa is routinely used to denote either thermal conductivity or relative dielectric constant (and for the latter, the usage is indeed common in EE and MSE, whereas in Physics epsilon might be more common). In the absence of specific references, I would argue using kappa instead of sigma may be so rare that it does not deserve being mentioned in wiki. (Of course, any property can be denoted by any letter in someone's work, that the author's choice and if it passes by a referee it does not automatically turn such a notation into a convention!) On the other hand, given the similarity of the names "(electrical) conductivity" and "thermal conductivity" and the widespread use of kappa for the latter, even suggesting to use kappa to denote the former is worrisome. Definitely there is no justification that the current version has "kappa=1/rho" instead of "sigma=1/rho" in the heading section, that is bordering vandalism. 157.93.254.201 (talk) 03:50, 30 April 2024 (UTC)

That you have made an effort to verify the claim about the use of kappa, and not met with success, surely justifies slapping a citation needed tag on the claim. I have reverted the change of sigma to kappa in the info-box. catslash (talk) 21:40, 4 May 2024 (UTC)