Talk:Coulomb

message: Does coulomb imply positive or negative charge?  Since the ampere per second is conventional current, would it technically be 6.24×1018 times the charge on a proton? - Omegatron 16:36, May 26, 2004 (UTC)
:I think you're probably right. However, I think it probably also makes sense to say "1 coulomb of electrons", knowing that this is the same as -1 coulomb of conventional charge. -- Anon
:: Er ... I think "does coulomb imply positive or negative charge?" is as meaningful a question as is "does meter imply positive or negative distance?" (or rather, displacement, so that we can actually allow negative values). A unit in itself has no sense of direction, positive or otherwise; it's just a measure of the magnitude.
:The charge of the electron is defined to be negative and the Coulomb is the SI derived unit for electrical charge, therefore a charge of 1 C cannot be from an excess of electrons. (See the definition of elementary charge.) Treating electrons as positively charged is a definitional error which could lead students consulting this article seriously astray. I have changed the references to electrons to protons where appropriate in the article to correct this, and added a reference supporting the correct view. Enon (talk) 23:12, 17 May 2010 (UTC)
thread_title: Untitled

message: "The Ampere is in fact a derived unit..." but not according to the Wikipedia entry for Ampere, where it says, "Because it is a base unit, the definition of the ampere is not tied to any other electrical unit."
Given the definition for the Ampere as given in the Ampere entry, I'm inclined to believe that the Ampere is in fact the base unit and the Coulomb is the derived unit, despite the relationship 1 A = 1 C/s.
:Correct.  The current SI standard defines the ampere as a base unit, for practical reasons.  (It is more intuitive to think of the charge on one electron as fundamental unit on which to base the definition of the Coulomb and then base the Ampere upon the Coulomb, but that's not how things are defined in current SI.)
:I am suspicious of the article section: "The ampere was historically a derived unit - being defined as 1 coulomb per second. Therefore the coulomb, rather than the ampere was the SI base electrical unit," because what I have read of the history of electrical units did not say that the ampere was figured from coulombs.  Here are pages about the history of electrical units:
:http://alpha.montclair.edu/~kowalskiL/SI/SI_PAGE.HTML
:http://www.sizes.com/units/ampHist.htm
If no one has any good reference that contradicts those references, I shall in time remove or replace the sentences. Nicknicknickandnick 08:54, 28 October 2007 (UTC)
replies: text: I believe the coulomb USED to be the SI unit, but it has been changed to the Ampere.  —Preceding unsigned comment added by 211.28.52.64 (talk) 07:01, 4 July 2009 (UTC)

text: No, the Coulomb *is* the SI unit for charge.  The NIST literature specifically states that SI units include both the base units and the derived units.  (And anyhow, if Coulomb isn't an SI, unit, then what is the SI unit for charge?  Faradays?  Abcoulombs?  Nooo.)   Coulomb is an SI unit.  But it's not measured directly as in the day when charge was standardized to a certain gram-ionic weight of monovalent ions (where one Faraday of charge passed through a molten-salt NaCl cell will deposit one mole or 23 grams of Sodium on an electrode.128.95.172.173 (talk) 01:56, 29 October 2010 (UTC)
thread_title:  Historical Note re derived unit 

message: Oh grow up! N^O^el (talk) 06:45, 5 March 2008 (UTC)
thread_title:  Constant vandalism 

message: It would be nice to have a real-world explanation of how much energy 1 Coulomb is.N^O^el (talk) 06:47, 5 March 2008 (UTC)
replies: text: Charge is not energy.  However, inside copper metal, one coulomb of mobile charge occupies a cubic volume 0.42mm on a side.  When coulombs are flowing through wires, each Coulomb is a little blob about 1/64" across.  This immediately makes you suspect that one Ampere, or a Coulomb per second, is a very slow flow.  After all, most wires are lots wider than 1/64" in diameter.  128.95.172.173 (talk) 02:11, 29 October 2010 (UTC)
replies: text:  Cool.  I never thought of it that way. This is my "What I learned on Wikipedia this week" item for the week. If you had a reference for this, I'd love to have it in the article; this sort of vivid physical example helps a lot. (Running the arithmetic myself shows that it's correct, asssuming one conductin band electron per copper atom...but I daren't post my calculations because the OR bigots will be on me.) --Wtshymanski (talk) 13:57, 29 October 2010 (UTC)

text: Zero. A coulomb is a measurement of charge, not energy. But it would be useful to know how much charge it is (e.g. how much charge your common or garden AA cell holds; that sort of thing). 212.137.63.86 (talk) 12:14, 6 August 2008 (UTC)

text: Isn't charge a measure of stored (potential) energy?  The stored energy in a battery is converted to kinetic energy (amperage) which does actual work (turns on a light) Tocksin (talk) 12:30, 27 March 2009 (UTC)
replies: text: No, charge has nothing to do with energy, and if you know the amount of charge, you cannot calculate the amount of energy.  Analogy: charge is like water.  Water can be stored behind a dam, or water can flow in a hydraulic system.  But water isn't a kind of energy; water isn't measured in KWH or Joules!  Neither is charge.  But if you know the water pressure and flow rate, you can measure the amount of work being done or the amount of hydraulic energy stored or transferred.  Same with charge: if you know the PD in volts and the total amount of Coulombs of charge transferred, then you can calculate the amount of work that was done or the amount of electrical energy stored or transferred.   But if the charge was transferred at zero volts, then no energy was transferred, only charge.128.95.172.173 (talk) 02:11, 29 October 2010 (UTC)
thread_title:  Real-world example 

message: According to Teach Yourself Electricity and Electronics Third Ed 1 coulomb = ~6.24 x 1018 electrons or holes. A current of 1 coulomb/1 sec = 1 amp. I find this definition a lot easier than the current one though it seems less precise. Could someone with more knowledge edit this page to include the definition that I've included, or explain why this definition was not included?. --69.235.4.174 (talk) 08:47, 31 May 2008 (UTC)
replies: text: It's not included because it's not the definition. JIMp talk·cont 08:33, 8 February 2010 (UTC)
thread_title:  Better Definition? 

message: I would like to propose adding the Q=It equation found on the Ampere page on this page, as Q also represents Coulombs.
I feel that this would help clear some confusion I personally experienced initially, which was why there where two different symbols (C and Q) for the coulomb.
Or is there some reason why its not there? 209.129.16.5 (talk) 04:17, 3 February 2009 (UTC)
replies: text: The symbol for coulomb is C.  Q is used in that equation as a symbol for charge - which is measured in coulombs. A variable in an equation is (hardly ever) symbolized by the abbreviation for the SI unit for measuring that variable.  Anyway, Q=It is a special case where the current is constant. --Wtshymanski (talk) 15:30, 3 February 2009 (UTC)
thread_title:  Unit Symbol 

message: Why are zeptocoulomb (10^-21) and yoctocoulomb (10^-24) listed when a single electron has a charge of about 1.602 x 10^-19 coulombs and the smallest quark charge is 1/3 of this? Is there something I'm missing here? --<SPAN STYLE="font-family:monospace; color:#008800; background-color:#ffffcc; border:1px solid #ff4444;"> B.D.Mills </SPAN> (T, C) 10:37, 2 March 2009 (UTC)
replies: text: Because some editors think that every SI prefix *must* be attached to every SI unit, disregarding actual usage, common sense or physical realizability to anyone other than astronomers or string theorists. I burnt on on this one about 2 years ago, but you're definitely on the right side on this one, in my opinion. --Wtshymanski (talk) 14:27, 2 March 2009 (UTC)
thread_title:  zeptocoulomb and yoctocoulomb? 

message: In principle, the coulomb could be defined in terms of the charge of an electron or elementary charge. ... . A coulomb is then equal to exactly 6.241 509 629 152 65 × 1018 elementary charges.
Elementary_charge  It has a measured value of approximately 1.602176487(40)×10−19 coulombs.[2]
???????????//  —Preceding unsigned comment added by 123.24.118.155 (talk) 03:07, 18 November 2009 (UTC)
replies: text: I rewrote this part, I hope it's clearer now. The quote before was inaccurate, no one to my knowledge has proposed "6.241 509 629 152 65 × 1018 elementary charges" as a redefinition (unlike a different numerical expression which has been proposed, it's a ratio of two exact numbers). I also tried to clarify that the discussion concerns different unit systems. --Steve (talk) 21:30, 29 January 2011 (UTC)
thread_title:  units 

message: "-6.24151×1018 electrons"
Since it makes no sense to have a negative number of electrons, and units are typically treated as magnitudes, not vectors, shouldn't this be positive? 71.55.0.14 (talk) 05:34, 29 January 2011 (UTC)
replies: text: Hope it's OK now (thanks Wtshymanski‎). --Steve (talk) 21:30, 29 January 2011 (UTC)
thread_title:  Negative number of electrons? 

message: Hi Wtshymanski,
I made this edit, which you undid here. The explanation was "not the way the coulomb is defined". Can you say more specifically what it is that I wrote that is wrong? Are you disagreeing with my "Definition" section, or my "Relation to elementary charge and "conventional Coulomb"" section, or both? Whichever it is I will be happy to supply references, I don't believe I wrote anything that isn't standard and universally accepted.
Also, you put in a template, "This section does not cite any references or sources," in a section that cites two sources! In the future I suggest the  template would be a better choice. Or do you think the current citations are invalid? I can see that the battery capacity claim should have a citation, but I don't think the Coulomb's law claim needs one, it's a straightforward calculation that anyone can check. (BTW right now that example is in the article twice! You restored it without re-deleting it from the other place.) --Steve (talk) 22:43, 29 January 2011 (UTC)
thread_title:  "Not the way the coulomb is defined"? 

message: https://www.youtube.com/watch?v=Lx64cq0HeXY  — Preceding unsigned comment added by 2601:242:4000:6A2:D866:2B7F:117F:B60 (talk) 18:13, 5 December 2015 (UTC)
thread_title:  Lec 01: What holds our world together? | 8.02 Electricity and Magnetism, Spring 2002 (Walter Lewin) 

message: Substituted at 12:20, 29 April 2016 (UTC)
thread_title: Assessment comment

message: In the referenced SI document, we have "la charge élémentaire e est égale à exactement 1,602 17X × 10−19 coulomb", which leads me to wonder (1) where all the other digits come from, and (2) does this imply that there will never be any more refined measurements of q_e? Can we at least find a better reference for q_e? Peter Chastain [¡hablá!] 07:03, 12 April 2020 (UTC)
thread_title:  Elementary charge exactly 1.602176634×10−19 coulombs? 

message: 1/1.602176634e-19 ≠ 10e19/1.602176634
98.195.237.62 (talk) 04:54, 4 July 2022 (UTC)
thread_title:  Maths incorrect...