Talk:Elementary charge

Sometimes "q" instead of "e"

The symbol is sometimes "q" instead of "e". See Boltzmann_constant#Role_in_semiconductor_physics:_the_thermal_voltage. This should be mentioned. Andries (talk) 12:06, 20 April 2014 (UTC)

SI to adopt Elementary Charge as determining Ampere

In 2018, the SI org CIPM is planning to discard the ampere-balance, and instead use Quantity of Electricity (in the form of the elementary charge,) to determine the Ampere. Be prepared to add a bit about this in a couple years. https://en.wikipedia.org/wiki/Proposed_redefinition_of_SI_base_units — Preceding unsigned comment added by 71.37.36.149 (talk) 22:45, 22 May 2016 (UTC)

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HEP

What on earth is HEP meant to mean? Even Google doesn't know, and wiki doesn't ... The given value 0.30282212088 happens to be ${\sqrt {4\pi \alpha }}=e/{\sqrt {\epsilon _{0}\hbar c_{0}}}$ and not merely ${\sqrt {\hbar c_{0}}}$ this is a real tragedy ... Thus the 1 HEP $={\sqrt {\epsilon _{0}\hbar c_{0}}}=e/{\sqrt {4\alpha \pi }}$C. Right? Ra-raisch (talk) 21:07, 12 August 2017 (UTC)

HEP is High energy physics, or particle physics the field that relies on quantum field theory where rationalized Lorentz–Heaviside units are used, in their naturalized form. Charge is not an independent dimension, as in Gaussian cgs units, so ε₀=1; and if you did not wish to naturalize the units, use plain ${\sqrt {\hbar c}}={\sqrt {197.3269788(12)~MeV~fm}}$ ones, as here. In most of the world of particle physics, these are the units used on account of their simplicity, elegance, and, you guessed it!, naturalness. If you wish, I could add a link to Lorentz-Heaviside, but please do not perpetrate plain wrong formulas in WP, which will only end up confusing more readers with inconsistencies and absurdities. Cuzkatzimhut (talk) 23:35, 12 August 2017 (UTC)

@Cuzkatzimhut: ok, I think a link to High-energy physics would be more appropriate. The dimension should be given with 1. Since most readers won't be familiar with HEP or LH-cgs, there should be more respect for SI, I am not bothered about non-metric systems popular in the US and UK. Most pages comparing or explaining the unit systems are grotty in this respect, lacking conversion tables, leaving constants . CODATA is a paragon and guideline in this respect. In this case here, the conversion factors MeV and fm are missing in the given unit: √ℏc/MeVfm) Ra-raisch (talk) 09:49, 13 August 2017 (UTC)

but even calculating $e/{\sqrt {\hbar c/(MeV~fm)}}=1.1405574270070711\cdot 10^{-20}$ and not the given value of 0.30282212088. I see no way of leaving ε₀ without introducing Z, R_K or other constants. Ra-raisch (talk) 10:36, 13 August 2017 (UTC)

I'm sorry, but you appear to be having a philosophical problem with Lorentz-Heaviside units, or cgs ones, and this is not a forum. Perhaps talking to a physicist in person, or reading up on HEP might help. As stated repeatedly, the elementary charge is a dependent quantity, defined as $e^{2}=4\pi \alpha ~\hbar c=(0.303)^{2}\hbar c$ in absolutely any $ML^{3}T^{-1}$units for ħc you may prefer. It is not in the units. Units are all interconvertible. HEP physicists, for 3/4 of a century, have been choosing to keep ħc in mind and insert it in the final answers handed over to engineers at the last moment. It is not rocket science. Please do not insert wrong formulas in the articles.Cuzkatzimhut (talk) 13:40, 13 August 2017 (UTC)

Well I don't like it that's true, but that is not the point. Your conversion is not(!) SI. No hidden factors bearing in mind! √4παℏc) = 5.3843840002589234e-14 m√N whereas e = 1.6021766208e-19 C. I think your rocket would miss the mars by wrong direction, dealing with manufacturers calculating in SI. And that is the guilty of the scientist not the manufacturer's. And as I said, wiki is not a platform of scientists but of ordinary people, using everyday language, measures and understanding. I found the correct conversion but you didn't like it: ${\sqrt {\epsilon _{0}\hbar c_{0}}}=5.290817647072351\cdot 10^{-19}$C. (ℏ=1.054571800e-34 Js, ε=8.85418781762039e-12 F/m).

$e_{HEP}{\sqrt {\epsilon _{0}\hbar c_{0}}}=e_{SI}=1.602176621160213\cdot 10^{-19}$ C and in SI ${\sqrt {4\pi \alpha }}=e_{SI}/{\sqrt {\epsilon _{0}\hbar c_{0}}}=0.30282212088$ and not merely √ℏc) = 1.7780682553250995e-13 m√N. So using √ℏc) may be correct in HEP but not in SI. Ra-raisch (talk) 15:03, 13 August 2017 (UTC)

The Vacuum permittivity ε₀ is necessary in all conversions to Coulombs, and perhaps you wish to devote your energies in that article. HEP physicists think of it as part of the definition of the Coulomb, in essence. If you convert $Nm^{2}$ to Coulombs squared, of course you will need it. But that is the beauty of the L-H system, that it never has to consider these conversions. It ends up measuring energies, times, momenta, etc... units linked to Newtons, Joules, seconds, etc... if you wished to talk to an engineer. Perhaps at the heart of this misunderstanding is the misplaced expectation that particle scattering will result in quantities involving Coulombs, as opposed to energies, angles, times... You never have to go there. I don't see why a layman would wish to go there, as some part of a notional fantasy, rockets and all. Cuzkatzimhut (talk) 16:37, 13 August 2017 (UTC)

I did not invent the equation g=e/sw, it is ridiculous in my eyes since g does not react with e. But the conversion of units is a completely different question. At least we agree at last, that ε must not be neglected in the conversion. That is all I said from the beginning, this was exactly what I requested, nothing more! ... so probably g=e/sw is to be understood by converting e(SI) to e(HEP) and taking g as a unit by itself. But how can these be compared by sw ... ok that is leading somewhere else. Ra-raisch (talk) 18:03, 13 August 2017 (UTC)

We only agree that ε must never be neglected in the conversion to Coulombs, part of whose definition it really is, but this is a conversion that I explained is not needed and has little point to it. By contrast, the standard picture involves SI units, Newtons, meters, ... that are used in their MeV, fm avatars. Indeed, g is the mother of all quantities, and, e is a derived quantity; this is at the heart of Electroweak unification: this is what we now know, but we did not in 1966 .. it suddenly all made sense, at last... Cuzkatzimhut (talk) 18:47, 13 August 2017 (UTC)

good, back to the article: 1) I understood now that √ℏc) is just the equation used in HEP in place of a unit and not to be taken for a conversion to/from SI. I guess this is confusing for anybody not familiar with HEP. I am not sure though how to clearify this in the expression, but may-be like this: √ℏc)[HEP]. 2) A little more explanations could/should be given in the page of HEP. 3) On the now linked page (LH-units), HEP is not mentioned at all. Ra-raisch (talk) 19:59, 13 August 2017 (UTC)

OK, I did something for a start. Your point that they had to be showcased up front in the L-H article is a good one. (Personally, I believe the string theory sentence there is correct but pompously silly--I would not object to it disappearing.) Here, my gut reaction is precisely to prevent going through metrology and systems of units, etc... The point of the box is to give the reader a quick tablet of reliable facts. Cuzkatzimhut (talk) 20:28, 13 August 2017 (UTC)

beautiful Ra-raisch (talk) 21:50, 13 August 2017 (UTC)

symbol for elementary charge

I'm not going to make any changes to the current footnote 2 by User:Headbomb -- I think this is a minor point. I happen to agree that mathematical constants should be set in roman, so that e=2.71828... would be distinguished from the elementary charge. (This is in fact what the IUPAC and IUPAP recommend.) However, I don't agree with the assertion that they are usually distinguished typographically in practice. At least in the U.S., the majority of professionally typeset work sets the mathematical constant e in italics, contrary to the comment in User:Headbomb's revert -- thus, the potential for ambiguity continues to exist. Alsosaid1987 (talk) 09:50, 16 June 2019 (UTC)

It is quite confusing to write the elementary charge as Euler's number $e$. Nobody does that in quantum physics or quantum chemistry. Furthermore, previously someone has written $q_{\text{e}}=-e$ and $q_{{\text{e}}^{+}}=+e$. This is an inconsistent notation! If you write the positron as ${{\text{e}}^{+}}$ then you should write the electron as ${{\text{e}}^{-}}$. Based on the latter remark, I have corrected the text to $q_{{\text{e}}^{-}}=-e$. I recommend strongly that the person who used the Euler's number $e$ to write the elementary charge, to update the text troughout with the best notation which is $q_{e}$ = "charge" $q$ + "elementary" $e$. In other words, the notation $q_{e}$ means "charge_elementary", and does not mean "charge_electron", which as I already explained has to be consistently written with the electron symbol ${{\text{e}}^{-}}$. Danko Georgiev (talk) 08:29, 20 August 2023 (UTC)

Nobody does that in quantum physics or quantum chemistry. I beg to differ, in my experience (from condensed matter physics), e is the most common notation. Whether it is confusing or not is a matter of personal taste.

But we should not argue based on personal experience, since such discussion would be doomed from the beginning. Here is a short survey of some sources. Standard bodies:

• The elementary charge is one of the defining constants of the SI system. SI brochure uses the symbol e for it. (SI brochure, p.127)
• Other standard bodies such as IEC (electrical technology) and IUPAC (chemistry) follow SI recommendations and use e in their publications.

Quantum mechanics textbooks:

• Griffiths, inside cover, Charge of electron: $-e=-1.60218\times 10^{-19}C$
• Sakurai uses e generally for charge, I did not find mention of the elementary charge
• Cohen-Tannoudji, inside cover, uses q for electron charge
• Schiff, p.471, e for electronic charge
• Landau & Lifshitz, p.116 The atomic unit of charge is $e=4.80\times 10^{-10}{\rm {esu}}$

Some more specialized sources:

• Kittel, Solid State Physics: uses e for "proton charge" (this is an old edition, but the never ones use the same notation)
• Coleman, Introduction to Many-body Physics: $e=-|e|$ denotes the magnitude and the sign of the electron charge (tells somewhat apologetically that this a common sign convention in older russian texts on the subject)
• Atkins, Physical Chemistry: e for elementary charge (Atkins' more advanced quantum chemistry books also use the same notation)

The notation $e$ is clearly the most popular within this sample, and is also the standardized notation. I see no support for $q_{e}$. No doubt it is used by some (e.g. Danko Georgiev), but it may not be relevant enough to be mentioned it in the introduction. Jähmefyysikko (talk) 13:21, 3 September 2023 (UTC)

In my opinion, it might be useful to revert to this version of the introductory paragraph. The current one gets sidetracked and discusses the notation too much. Jähmefyysikko (talk) 13:33, 3 September 2023 (UTC)

Majority of academic physical journals will not publish articles where e is used for elementary charge. Here are just a few Open Acess articles in high impact physical journals that show widespread usage of $q_{e}$ for elementary charge:

• Hofmann, Oliver T. and Deinert, Jan-Christoph and Xu, Yong and Rinke, Patrick and Stähler, Julia and Wolf, Martin and Scheffler, Matthias (2013). "Large work function reduction by adsorption of a molecule with a negative electron affinity: Pyridine on ZnO$(10{\bar {1}}0)$". The Journal of Chemical Physics. 139 (17): 174701. doi:10.1063/1.4827017.{{cite journal}}: CS1 maint: multiple names: authors list (link)
• Levko, Dmitry and Arslanbekov, Robert R. and Kolobov, Vladimir I. (2019). "Modified Paschen curves for pulsed breakdown". Physics of Plasmas. 26 (6): 064502. doi:10.1063/1.5108732.{{cite journal}}: CS1 maint: multiple names: authors list (link)
• Horný, Vojtěch and Veisz, László (2021). "Generation of single attosecond relativistic electron bunch from intense laser interaction with a nanosphere". Plasma Physics and Controlled Fusion. 63 (12): 125025. doi:10.1088/1361-6587/ac2996.{{cite journal}}: CS1 maint: multiple names: authors list (link)

I do not accept your cherry picking. If we select an academic physics journal and perform unbiased statistics on all journal articles published in a recent year, say 2022, majority will be using $q_{e}$ for elementary charge and almost none will be using italic e. Danko Georgiev (talk) 08:04, 11 September 2023 (UTC)

No cherry picking was involved. I chose the textbooks that seemed the most popular for general QM, condensed matter physics, and physical chemistry, and reported all the findings to you. The claim that Majority of academic physical journals will not publish articles where e is used for elementary charge is simply not true. If you look at recent papers published in Nature, Science or Physical Review Letters (links are to searches) you will find counterexamples. Here's one for each journal: [1][2][3]. In the above searches, you do find articles that use other notations such as $q$, $q_{e}$ or $e_{0}$, but $e$ seems to be the most common. Jähmefyysikko (talk) 22:05, 11 September 2023 (UTC)

Examples of "bad notation" and "bad writing" are just that: "bad". Good writing requires that a single symbol is not used for two different things. Griffiths is definitely not an example of good writing, as in Problem 1.8 on page 13 he clearly uses formula with italic e to denote Euler's number, not the electron charge e. Good writing is understood by a noob who checks the textbook inside cover for the notation and then goes on to read the formulas inside the main text. In Griffiths textbook, a noob can check the inside cover and see that e is the electron charge, and then going to Problem 1.8 on page 13 will read off that the wavefunction is given by the electron charge to some power. Mocking the noob for his lack of knowledge is not good because the fault is in the textbook, namely, textbooks are expected to be read by noobs who lack knowledge. Things that are "not good" need to be changed. I am trying to help all previous Wikipedia editors who tried to explain that the notation e is "bad notation". There are modern authors who try to promote good writing with good notation, and my works are not the only example of this kind. If we are going to do cherry picking, I can post multiple textbooks who use $q_{e}$ for electron charge. Here is a good online textbook for Physical Sciences Grade 10 (not written by me) that uses the good notation $q_{e}$. Danko Georgiev (talk) 07:27, 11 September 2023 (UTC)