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Archives

/Archive 1 /Archive 2

On the consideration of establishing a clearer understanding of Ohm's law from the vantage of the quantum movement of electrons, note that electrons either move at the speed of light or don't, unlike the fluid in a pipe. The speed of electron flow in a wire seem, to me to be constant. Therefore I have posted this, not only to start a discussion on this subject but to have answered my own questions from any quantum expert authorities out there to fulfill my personal unknowns because knowing very precisely how electrons actually move in a wire as amperage and exactly what voltage is that powers them and how and and actually what "resistance" is, quantumly speaking, to me is a mystery and fogs my actual understanding of ohm's law and makes me uncomfortable with it, at all. In short, I need to reconcile quantum theory to Ohm's law (I don't seem to be getting that here).

It seems, to deeply and completely understand quantum concepts about voltage one would need to know what's going on inside the atom and how electrons actually begin then, thereafter continue to "flow" or "jump", if you will from atom to atom (or flow over them or both). It would seem that when the magnetic equilibrium of an atom or a group of atoms becomes disturbed when they come together to form compounds or through electromagnetic induction there becomes a magnetic pushing or pulling of electrons from one area to another which constitutes electron flow. Quantum theory seems to present that they are all jumping instead in and out of a string of atoms simultaneously. However, I would rely upon you expert quantum gurus out there to tell me exactly how they go through a wire.

Does an electron pop into a copper atom on one end of the wire and another pops out the other side of that atom and into the next and the 186 k miles per second speed of electron flow equate to the speed an electron can orbit around to the other side of all the atoms in the chain or does one pop in one side of an atom, cross the atom at 186 miles per second as the others in the chain do the same,simultaneously and an electron pops out the other end of the wire (after different electrons in that same unit of time all pop out of the exit side all in one motion in the atom chain). Is 186 miles per second the speed it takes for one electron to travel by itself in one second across a wire or is it the time it takes for all the electrons in a chain to travel across one atom respectively?

Does increased voltage cause increased numbers of individual electrons in individual streams to "jump" through the wire with each electron having its own path? What happens with the electron "flow" or "jumping" when a variable resistor is opened very slowly like a faucet would be, exactly? I wish someone could actually make an animation of electron flow within actual known ohm's law circuit lessons with wires magnified so they look like pipes when you zoom into them and they become as large as your screen and you can see how they go around tight turns in the wires like they were pipes. This whole subject fascinates me but frustrates me at getting at the factual answers. However, I feel that quantum flow of electrons, if one understands all about it would bring about a complete understanding into what electricity is, and how it works within the Ohm's law equations and would bring forth a complete "Ohm's Law" definition, not here now and certainly would be very useful and worth while because I'm not getting that full and complete definition and understanding with that left out.

Also, what needs being answered before all that is why atoms "jump" at all within an atom, one would think instead of variably changing states (in layman's words please).

Thank You. — Preceding unsigned comment added by 71.178.201.92 (talk) 02:34, 31 October 2012 (UTC)[reply]

Electrons do not move at the speed of light, even when their associated electromagnetic waves do. It's hard to explain QED in layman's language, but there are books on it. Dicklyon (talk) 03:18, 31 October 2012 (UTC)[reply]

Electrons move close to the speed of light in copper and in air pretty much at it, right? I had one expert tell me the photon is created by orbiting electrons at a certain speed changing energy levels releasing a photon at that speed in the EM spectrum. Nonetheless, they are not slowed signifigantly by anything with resistance just stopped. — Preceding unsigned comment added by 71.178.201.92 (talk) 06:22, 31 October 2012 (UTC)[reply]

As Dicklyon says, electrons do not move at the speed of light in copper wires. The average drift velocity in copper is slower than a sick snail. Typical copper cables transmit signals at around 2/3 light speed but the electrons hardly move. Please take further questions on the subject to the Science reference desk, the page here is to discuss improvements to the article, not answer people's questions. SpinningSpark 09:53, 31 October 2012 (UTC)[reply]

The IV curve for battery seems wrong. For larger currents the voltage should drop and viceversa you should need higher than nominal voltage to charge a battery.

I understand what you are saying; that would reflect how batteries act under a varying load. However, an I-V curve is normally made by applying a varying voltage to the device and measuring the resulting current. Thus the voltage is the independent variable (x-axis), the current is the dependent (y-axis). So the curve shown is correct: as the voltage rises above the battery's current terminal voltage, current flows into the battery (increasing positive current); as it falls below that, current flows out of the battery. The point where the curve crosses the X-axis is the point where the applied voltage matches the battery's. Thus the curve is correct and consistent with how the others were measured. You are proposing that current would be the independent variable and voltage the dependent. I'm not sure how you make current from a battery an independent variable. It seems to me you'd need a variable R for a load, then the true independent would be the R value and both I and V would have to be plotted as dependent. Jeh (talk) 17:58, 26 March 2014 (UTC)[reply]

In the plot, I<0 is the ordinary direction of current when using the battery. I>0 would be recharging the battery. The questioner would like to flip the sign convention so that I<0 would be recharging the battery. Well, for this plot, flipping the sign convention is not really an option, because then the four different plots would be inconsistent with each other. The plot is correct as is. --Steve (talk) 18:54, 26 March 2014 (UTC)[reply]

That's an important clarification too, Sbyrnes321. Positive current for all of the other devices represents the normal direction: Electrons leave the negative terminal of the external supply, and return through its positive terminal. (Or, if you prefer classical current flow, positive means that current-ons ;) are leaving the supply positive terminal, flowing through the load, and returning through the negative terminal.) We use the same convention for the battery.

However, it is not just that. The OP's statement that "for larger currents the voltage should drop" refers to how batteries behave when you measure them under load. It's due to the battery's internal resistance, of course. For that matter the graph here doesn't reflect changes over time as the battery is charged or discharged. But an important part of the answer is simply "that's not how I-V graphs are made". Jeh (talk) 19:08, 26 March 2014 (UTC)[reply]

I had in mind to use the convention for active elements for the battery and the convention for passive elements for the loads (http://en.wikipedia.org/wiki/Passive_sign_convention#Alternative_convention_in_power_engineering) while the four plots follow the passive sign convention (http://en.wikipedia.org/wiki/Passive_sign_convention#Sign_conventions). May be one could write that the plot uses the Passive sign convention. If one makes a plot with V=constant to represent an ideal battery there will be no misunderstanding anymore. — Preceding unsigned comment added by 2.230.128.127 (talk) 19:46, 26 March 2014 (UTC)[reply]

BTW: in the plots axes have arrows on both sides. That's a bit unusual.

Yes, we can add a sentence

"(The plots use passive sign convention.)"

at the end of the caption. I don't really like it though. The caption is saying something very very simple: What is Ohm's law. It's a clear message for readers who are not experts, indeed readers who may know almost nothing about electricity, and who may have never heard the phrase "sign convention". Adding that parenthetical would make the caption harder to read, more jargon-y, for those readers. It would not improve understanding of Ohm's law, which is after all the point of this article.

And anyway, as far as I know, using the passive sign convention is generally regarded as a legitimate and not-especially-unusual thing to do. So it doesn't desperately need an apology or disclaimer.

On the other hand, in an article like Current–voltage characteristic, it is a very good idea to say that this is the passive sign convention, and indeed I just did so! :-D --Steve (talk) 00:02, 27 March 2014 (UTC)[reply]

I fixed the arrowheads in the diagrams. SpinningSpark 11:29, 27 March 2014 (UTC)[reply]

Thank you!! --Steve (talk) 12:37, 27 March 2014 (UTC)[reply]

request to remove wikihow reference. it's a SPS (and an inline url reference)

WP:SOFIXIT. And btw, please sign your talk page comments. Jeh (talk) 23:14, 24 April 2014 (UTC)[reply]

Good call. I removed it. Next time you have a good idea for an edit, just do it. Dicklyon (talk) 04:45, 25 April 2014 (UTC)[reply]

Ok thanks. FYI, I couldn't fix it because it's locked (and I think I don't have enough edits). Nearwater (talk) 05:02, 25 April 2014 (UTC)[reply]

Could you add "provided temperature remains constant" to : Ohm's law states that the current through a conductor between two points is directly proportional to the potential difference across the two points "provided temperature remains constant"

I'm a student in Singapore and my teacher's notes and textbooks emphasize the "provided temperature remains constant" part. 122.11.255.163 (talk) 15:27, 6 October 2014 (UTC)[reply]

Not done: This is not uncontroversial. Please read previous discussions on this in the archives first. If you still think it should be changed after that, then give your reasoning here. SpinningSpark 22:42, 6 October 2014 (UTC)[reply]

(Mainly Talk:Ohm's law/Archive 2#What a lot of rubbish.) --Steve (talk) 14:24, 7 October 2014 (UTC)[reply]

Please change the Tagalog translation of this article from this Ang batas ni Ohm ay nagsasaad na ang kuryente na dumadaan sa isang konduktor sa pagitan ng dalawang mga punto ay tuwirang proporsiyonal sa diperensiyang potensiyal sa ibayo ng dalawang mga punto. Ito ay nagpapakilala ng konstante ng proposiyonalidad, resistansiya,[1] at inilalarawan ng ekwasyon na :[2]

I = V/R, kung saan ang I ang kuryenteng dumadaan sa konduktor sa mga unit ng ampere, ang V ang diperensiyang potensiyal sa ibayo ng konduktor sa mga unit na volt at ang R ang resistansiya ng konduktor sa mga unit ng ohm. Sa mas spesipiko, ang batas ni Ohm ay nagsasaad na ang R sa ugnayang ito ay hindi nagbabago at hindi nakasalalay sa kuryente.[3]

to this

Sinasaad ng Ohm's Law na ang kuryenteng dumadaan sa talaytayan sa pagitan ng dalawang punto ay tuwirang proposyonal sa potential difference sa pagitan ng dalawang puntong ito. Gamit ang resistance bilang konstant ng proporsyonalidad, makukuha ang karaniwang matematikal na ekwasyong nag-uugnay sa mga ito:

I=V/R, kung saan ang I ay ang kuryenteng dumadaloy sa talaytayan na nasusukat sa amperes, V ang potential difference sa magkabilang dulo ng talaytayang nasusukat sa volts at R ang resistance ng talaytayang nasusukat naman sa ohms. Higit pa rito, sinasaad ng batas ni Ohm na ang R sa ugnayang ito ay hindi nagbabago at hindi nakadepende sa kuryente.

Ang batas na ito ay ipinangalan sa pisisistang Aleman na si George Ohm na sa isang nalathalang kasulatan hinggil sa kaalaman noong 1827 ay naglarawan sa mga sukat ng inilapat na boltahe at simpleng elektrikal na sirkit na naglalaman ng iba’t ibang haba ng kawad ng kuryente. Nagpakita rin siya ng ekwasyong bahagyang mas komplikado upang ipaliwanag ang resulta ng mga eksperimento.

Sa pisika, ang terminong Ohm's Law ay ginagamit din upang tukuyin ang iba’t ibang mga pangkalahatang pahayag ng batas na naunang binalangkas ni Ohm. Ito ang pinakapayak na halimbawa nito:

J=σE kung saan ang J ay katumbas ng current density sa isang lokasyon sa loob ng isang materyal na may mataas na sukat ng resistance, E ay ang electric field at ang σ (Sigma) ay ang conductance. Muling binalangkas ang Ohm's Law dahil kay Gustav Krichhoff.

because some of the terms like resistance, potential difference, Ohm's Law and many other more should be written in its English term even in Tagalog translation. Tricia Cristal (talk) 21:36, 24 June 2015 (UTC)[reply]

This is the English language Wikipedia. You'll need to go to the Tagalog Wikipedia page at tl:Batas ni Ohm and make the change there. As I don't think that page is protected, and as you have Tagalog language skills, you can go and make the change yourself. Andy Dingley (talk) 21:45, 24 June 2015 (UTC)[reply]

Reference 7 has a dead (?) link. Leads to an error screen. — Preceding unsigned comment added by 130.65.254.5 (talk) 18:46, 2 March 2016 (UTC)[reply]

Re [1] etc.

I would support this edit, and the others like it. Formatting of the symbols should match, between the body text and the equations set in LaTeX. That means using {{math}} in the body text, even for single characters. Andy Dingley (talk) 23:46, 22 January 2017 (UTC)[reply]

I don't have a problem with using the templates to get the fonts to match (well kind of nearly ugly match). The issue is the editor first tried to bold everything, and then tried to unbold everything when that was reverted. That is wrong, and so is taking the italics off variables. There might be something that can be improved there, but this editor is not achieving that. SpinningSpark 00:09, 23 January 2017 (UTC)[reply]

The editor has fewer than 100 edits on English Wikipedia. I would suggest the editor, while clearly well-intentioned, should back off on these formatting issues until s/he is more familiar with the conventions here. As it is s/he is creating much unnecessary cleanup work for no benefit to the readers. Jeh (talk) 04:23, 23 January 2017 (UTC)[reply]

I mean... here are the net results of the last sixteen edits - three of them by SpinningSpark, the rest by the new editor, creating the errors that SpinningSpark was fixing. Jeh (talk) 09:44, 23 January 2017 (UTC)[reply]

Then perhaps the two of you could find the time to "just do it right", rather than everyone going in circles with simple reversions? (And I know that's often an awkward thing to spontaneously ask).

Would you agree my point that {{math}} is appropriate even inline for single characters, as the way to get the formatting synchronised between body and pull-equation typesetting? Or do you think that "body text has no applied formatting", as some styleguide simplicity issue? Andy Dingley (talk) 12:42, 23 January 2017 (UTC)[reply]

@Frank Klemm: please stop changing the math formatting until you have discussed it here first. You clearly do not unserstand the conventions of mathematical presentation. J and E are vectors which are presented in an upright bold font. All your changes to the formatting so far have been wrong. Please stop changing it. SpinningSpark 14:20, 23 January 2017 (UTC)[reply]

If this attempt fails, we can always get the page semi-protected. Jeh (talk) 15:47, 23 January 2017 (UTC)[reply]

We should need vector proof of it Babymadox (talk) 03:48, 13 February 2017 (UTC)[reply]

Please change

There are, however, components of electrical circuits which do not obey Ohm's law; that is, their relationship between current and voltage (their I–V curve) is nonlinear (or non-ohmic). An example is the p-n junction diode (curve at right). As seen in the figure, the current does not increase linearly with applied voltage for a diode. One can determine a value of current (I) for a given value of applied voltage (V) from the curve, but not from Ohm's law, since the value of "resistance" is not constant as a function of applied voltage.

To

There are, however, components of electrical circuits which do not have a direct relationship between current and voltage (their I–V curve) is nonlinear. An example is the p-n junction diode (curve at right). As seen in the figure, the current does not increase linearly with applied voltage for a diode. One can determine a value of current (I) for a given value of applied voltage (V) from the curve, the value of "resistance" is dictated by the applied voltage and current.Ohm's paper specifically covers devices whose resistance is changed by stimulating influences like current and voltage which would include diodes and other semi-conductors. The paper indicates that a circuit which includes such devices must be allowed to settle into a stable state before the "law" can be used. The paper also indicates that the notion that "the current in a circuit changes linearly with applied voltage" can ONLY be asserted in a circuit that does not contain non-linear components. Trevor German (talk) 21:41, 10 November 2017 (UTC)[reply]

I prefer the version as written. Trevor, I'm not sure I understand why you think we should be citing Ohm's paper here. Do you think that the article is slandering Georg Ohm by implying that he did not understand that there are nonlinear elements? If so, well I don't think the article is implying that, in fact the history section discusses this at length I think. Or do you think "Ohm's law" is by definition the exact law that Ohm wrote down and we are not properly describing it? If so, I disagree, I think this is an article about the thing that all modern engineers call "Ohm's law", and not about any particular historical equation or paper. If not, what are you getting at? Thanks, --Steve (talk) 02:03, 11 November 2017 (UTC)[reply]

Steve, The real issue is what we call Ohm's Law is really Maxwell's derivative of part of Ohm's work. And Maxwell left out non-linear devices. As such my edit suggestion is actually a bit off. According to Ohm, non-linear devices are handled, according to Maxwell, they are just ignored. It's a bit of a paradox. You may find my discussion here interesting. https://electronics.stackexchange.com/questions/339055/does-a-diode-really-follow-ohms-law/339059#339059 — Preceding unsigned comment added by Trevor German (talk • contribs) 20:29, 13 November 2017 (UTC)[reply]

If a reader believes the following:

This law is called Ohm's law, therefore (1) it was originally invented by Ohm and (2) it is exactly as Ohm originally understood and described it.

...then that reader has a misconception. This is not a valid inference. I would suggest that this reader should study and ponder Stigler's law of eponymy.

I think that you are proposing to re-scope the whole article to be compatible with this misconception. But I think that's the wrong approach. The right approach is to treat it as a misconception, and write a very good history section that corrects the misconception.

If you think that the history section is inaccurate, misleading, or incomplete in any way, I am very open-minded to hearing your suggestions. --Steve (talk) 14:00, 14 November 2017 (UTC)[reply]

Yes I guess that is what I am saying, and yes the notion of writing the whole thing in that light is the wrong approach.

And No, this page does seriously imply Ohm's Law is Ohm's.. when in fact it is not, it is, as written, Maxwell's Extrapolation Of Ohm's Law.

However, I believe it is indeed worth a mention that there is a real disjoint in there between Ohm's intent and Maxwell's definition.

Because of the latter, there is a great deal of argument about Diodes et. al.

I just have no idea how and where to go/start with that. — Preceding unsigned comment added by Trevor German (talk • contribs) 21:09, 17 November 2017 (UTC)[reply]

Not done: please establish a consensus for this alteration before using the {{edit semi-protected}} template. Galobtter (pingó mió) 11:08, 22 November 2017 (UTC)[reply]

It should be actually, "Ohm's law states that at a constant temperature, the current through a conductor between two points is directly proportional to the voltage across the two points. P.M.MENGHANI 08:41, 15 November 2017 (UTC) — Preceding unsigned comment added by Pavan.167869 (talk • contribs)

The proviso that temperature remain constant has been suggested many times on the talk page (see also Talk:Ohm's law/Archive 2) and has always been rejected. I think that's the right decision. Here are three reasons that convince me not to mention temperature:

(1) If we need to say "provided temperature remain constant", do we also need to say "provided strain remains constant", "provided the material remains constant", "provided that no magnetic fields are inducing voltages right now", etc. etc.?

(2) In general, saying that X is proportional to Y does not and should not preclude the possibility that X and Y depend on other parameters Z.

(3) If you are really in the situation of Thermistor#Self-heating effects, where resistive heating causes your circuit to show a significant level of nonlinearity and hysteresis, I personally would say that your circuit is not ohmic, i.e. that Ohm's law is not the right description of this circuit. --Steve (talk)

The formula says I = V / R which is wrong. V is a unit (volts), I and R is not. The proper Ohm's law is I = U / R. If it was to be written with units (which is not correct) it would be A = V / Ω (as you can tell it doesn't look like a formula you ever saw). In short, please change V to U in the places where it's used as part of a formula! — Preceding unsigned comment added by 62.20.114.197 (talk) 10:29, 17 February 2018 (UTC)[reply]

I disagree, I think it's correct and common to use V as a variable representing a voltage. It's usually obvious from context whether "V" means "volts" or "the variable V", or if it's not obvious from context, you can remember that the variable V is italicized and the unit V is not. I think V has the strong advantage of being the most common choice of variable name in this context, and that this outweighs any possible disadvantages related to people getting confused with the unit. Just my opinion. :-D --Steve (talk) 02:36, 18 February 2018 (UTC)[reply]

V may be quite common as symbol for voltage in some countries, but it is incorrect, as the symbol for voltage is U. [2] V is the symbol for electric potential. [3] Using the same abbreviation for the quantity and for the associated unit leads to a high risk of mismatch. Have a look at the USB equation as example:

V = 5 V | substract V

0 V = 4 V | divide by V

0 = 4 (f)

Using V will be understood in most cases, but it is sloppy nomenclature. --Gunnar (talk) 17:17, 8 June 2020 (UTC)[reply]

In my experience, living and learning in the USA, if you ask an electrical engineer what the correct variable name is for voltage s/he will almost certainly tell you "V". If you ask a physicist, s/he is likely to tell you "U", and may also tell you that the correct term is "potential difference". Either is acceptable. Joe Avins (talk) 14:15, 21 June 2022 (UTC)[reply]

Steve, you may easily disagree, but the important point is if you can make a point. You can name you table "chair" and your chair "table" and this will work for a while if your whole family or neighbourhood has the same habit of naming wooden things. But for a global project – and Wikipedia is a global project – we need to have clear terminology. And U is the symbol for voltage, whereas V is the symbol for electric potential. These two are closely related but not the same U = ∆V = V₁ - V₀. A difference in the potential (= voltage) is always relative but has a given bedrock e.g. the chosen V₀, whereas an absolute potential is sometimes difficult to zero. I am aware that many electrical engineers use V as a symbol for voltage = electric potential difference, but this is simply speaking sloppy behaviour which has been passed on from generation to generation. The very idea behind not using V for both the symbol of the quantiy and the symbol of the unit error reduction. You don't choose k as the symbol for mass because it resembles kilogram. Gunnar (talk) 22:53, 7 June 2021 (UTC)[reply]

This has been repeatedly discussed before (Talk:Ohm's law/Archive 2#Shouldn't it be E=IR rather than V=IR?, Talk:Ohm's law/Archive 2#U = I/R or V = I/R, but as usual, there is no reference to sources, only opinions and assertions. In the first discussion I gave the first four results from gbooks (mostly no longer previewable) which all use V. I'm getting similar results from a new search; [4][5]. My own basic college books also use V: Ward, Electrical Engineering Science; Hughes Electrical Technology. I think that's enough to show that English textbooks largely use V when describing Ohm's law. SpinningSpark 13:18, 12 August 2021 (UTC)[reply]

I like to submit a simplied version of the Ohm's wheel. The traditional version of 12 equations is reduced to 4 equations. The equations are reorganised to facilitate the use and it is much easier to understand and remember. I try to load a graphic but the file was rejected. Thank you for your help. Jo JoDelltek (talk) 05:23, 24 February 2018 (UTC)[reply]

 Not done for now: If you are having file uploading or media questions, then you can ask for help on those issues at Wikipedia:Editor assistance/Requests or Wikipedia:Media copyright questions, depending on whether you received just a generic upload error or a specific copyright error message. It is not likely, however, that even if you upload your image correctly that it will be accepted as an addition to this article. Please read the Wikipedia policy on original research. Wikipedia is not a publisher of original thought and what you're describing sounds like your own version of the equations involved. Even derivative original research is covered by that policy. I hope this helps. Eggishorn (talk) (contrib) 18:52, 24 February 2018 (UTC)[reply]

In Ohm's formula,

it is not immediately apparent how that relates to the modern form. I would like to add the following to the article. Please let me know if you support or object to this addition.

I don't have a source to say this is the right interpretation of Ohm's expression, but the internal resistance formula is well known and applying it here, I would argue, is covered by WP:CALC. By the way, this clearly shows that the word only should be dropped from "a depends only on the thermocouple junction temperature". SpinningSpark 18:52, 25 May 2018 (UTC)[reply]

There might be a missleading formalism in the section "Other Versions -> Conductive Fluids", where the difference of velocities of the electrons and ions is not written in vector form. I might be wrong with this but please check. — Preceding unsigned comment added by Paulufe (talk • contribs) 09:14, 22 October 2018 (UTC)[reply]

In the first of two graphics for an 'Ohm's law wheel', it appears to my uneducated eyes that a formula for amps in the top-right of the first graphic might be incorrect. Where it says P/R in the 'A' quadrant of the wheel, it should probably be sqrt(P/R), matching the black+white second wheel below it.

There's also a fishy-looking formula suffering the same problem in the 'V' quadrant of the wheel, for P*R. The other black+white chart says it's sqrt(P*R).

The presumably incorrect graphic is here: https://en.wikipedia.org/wiki/File:Basic_laws_of_Electrical_Engineering_v.3-1.svg

I have not checked the other formulas in the wheel for correctness, as I am ignorant on electricity. It might be wise to check all the other formulas while making any changes. This is just a heads-up, I haven't made any edits/corrections to actual page. Senquack (talk) 20:59, 29 July 2019 (UTC)[reply]

I've removed it. We don't need three diagrams of this sort anyway. Some say we shouldn't have any. SpinningSpark 22:29, 29 July 2019 (UTC)[reply]

Thanks! I do like the wheel personally, the remaining one is helpful FWIW --Senquack (talk) 01:00, 30 July 2019 (UTC)[reply]

The equation presented in the article is currently in the form

And the text interprets this equation by stating that current is proportional to voltage, with resistance as the proportionality constant.

For readers without strong algebra proficiency, it might not be obvious why resistance is in the denominator, since it's the scaling factor.

If the equation were instead presented as

Then I think it would be more intuitive that R is a proportionality constant that links I and V, as this takes the more familiar form of a linear equation,

Furthermore, the form is the way that I usually encounter Ohm's Law, but perhaps this isn't true in other fields.

Does anybody object to rearranging this equation to bring R to the top? Hadron137 (talk) 05:34, 19 May 2020 (UTC)[reply]

The current form suggests that V is the independent variable and I is the dependent. I'd write it both ways. Dicklyon (talk) 06:04, 19 May 2020 (UTC)[reply]

Please, let's not have multiple forms in the lead. That is already done in the body of the article. Littering the lead with too much math markup is very off putting to readers, and I don't believe for one minute that it will help to clarify anything. SpinningSpark 13:25, 19 May 2020 (UTC)[reply]

My own textbooks are not showing any particular preference for V=IR, and if we have to choose one, my vote is for I=V/R becasue that's the way Ohm stated it in Die galvanische Kette.

Die Grösse des Stromes in irgend einem homogenem Theile der Kette wird durch den Quotientienten bestimmt, den man aus dem Unterschiede der an den Enden dieses Theils vorhandenen elektrischen Kräfte und aus seiner reduzirten Lange bildet. The magnitude of the current in any homogeneous part of the chain is determined by the quotient formed by the difference in the electrical forces present at the ends of this part and its reduced length.

— Ohm, p. 36

where,

S is the magnitude of the current (Grösse des Stromes)

A is the difference in electrical forces (Unterschiede elektrischen Kräfte, potential difference)

L is the reduced length of the part (reduzirten Länge).

Ohm defined reduced length as the ratio of the real length of the part divided by the product of cross-sectional area and conductivity, ie, what we would call resistance. Of course, laws stated as they were historically formulated are not always understandable. If I were to state Newton's second law as Newton gave it (force is proportional to velocity) I would undoubtedly be told I am mistaken, but in this case there is no reason not to. SpinningSpark 15:28, 19 May 2020 (UTC)[reply]

Ohm's original conceptions and writing were messy, but a historian/editor arrived at a nice clean statement that expressed it both ways, in English translation, in 1891. See this book. I agree with not putting much math in th lead, but currently the other form is more than half way down, so not very accessible. Probably it belongs in the first section. Dicklyon (talk) 16:43, 19 May 2020 (UTC)[reply]

I don't deny that one can find numerous authors writing it both, or even all three, ways. It's not a question of sources, but of style, and in particular the style of keeping the lead simple and readable. I can only see your gbooks link in snippet (I'll flag that to google as something that is PD), but here it is at the IA. That could usefully be added in the references as a translation of Die galvanische Kette. But is that notation any less obscure than Ohm's? Using I for emf is hardly readily understandable by the modern reader.

I agree with you that the section on circuit analysis could usefully be higher up, possibly the first section, but certainly in front of "Microscopic origins" and "Hydraulic analogy". I would also say that some simpler material is either needed at the top of, or in front of, the history section. Launching straight into issues of internal resistance is not good for flow or reader comprehension. SpinningSpark 01:09, 20 May 2020 (UTC)[reply]

The choice of letters is not modern, but otherwise it seems cleaner than Ohm's ramblings. Putting first a simple explanatory section with the two (or three) ways of expressing the proportionality seems sensible to me. Dicklyon (talk) 03:57, 20 May 2020 (UTC)[reply]

Dicklyon made the point that the current form suggests that V is the independent variable and I is the dependent. This statement, to me, gives weight to the argument of stating the equation as V=IR, since current is a SI base unit, as defined by the modern interpretation. A base unit can hardly be dependent.Hadron137 (talk) 06:15, 24 May 2020 (UTC)[reply]

Your reasoning is a misconception. Base/derived units have nothing to do with independent/dependent variables. The graph here, for instance, has distance on the y axis. In this context distance is both a dependent variable and a base unit. Base units were chosen by the SI for the ease and accuracy with which a measurment standard could be constructed, not because they were somehow fundamental. In electrical science it is natural to consider charge to be the fundamental quantity, but nevertheless current is chosen as the base unit. In the case of Ohm's law, V and I are interdependent, either can be considered the independent variable depending on context. In a large number of cases we are dealing with a constant-voltage source, and voltage is the independent variable in that context. SpinningSpark 12:17, 24 May 2020 (UTC)[reply]

I agree with Spinningspark here. There's no reason the dependent variable can't be in base units. That's not the point I was making. Dicklyon (talk) 16:32, 24 May 2020 (UTC)[reply]

Well stated, thanks.Hadron137 (talk) 18:13, 24 May 2020 (UTC)[reply]

In [6], @Spinningspark: wrote 'There's no need to overcomplicate this. The "square" symbol is actually special use, meaning an inductance-free resistor. it's not especially relevant to this article)'. I can't refute this but haven't heard of this or find a source stating so and am curious where this convention comes from. Resistor#Electronic_symbols_and_notation gives the long rectangle as the IEC resistor symbol. Is this worth adding to the Resistor article, if there's a reputable source for it? Thanks, cmɢʟee⎆τaʟκ 23:13, 24 July 2020 (UTC)[reply]

I've restored your edit. Sorry, I completely misinterpreted what you wrote. There is a symbol that used "square" zigzags rather than triangles to indicate that a resistor was inductance free (see Ayrton–Perry winding) and for some stupid reason I thought that was what you were referring to. It may well not have been an official symbol of any kind and I haven't seen it for about 35 years. My memory is not what it used to be, but I believe it appeared in AVO circuit diagrams of their multimeters and I recall a lecturer explaining its meaning while I was an undergraduate. SpinningSpark 09:32, 25 July 2020 (UTC)[reply]

Thanks for explaining and restoring, @Spinningspark: Good to know about the use of Ayrton–Perry winding. Cheers, cmɢʟee⎆τaʟκ 00:24, 5 August 2020 (UTC)[reply]

Change formatting of vectorial velocities to bold face in Ohm's_law#Conductive fluids, first equation. Krystophny (talk) 17:35, 24 November 2020 (UTC)[reply]

@Krystophny: I have confirmed your account so you should now be able to edit the page yourself. Let me know if you are still having problems. SpinningSpark 11:13, 25 November 2020 (UTC)[reply]

Ohm's Law states that the current passing through the conductor between two points is directly proportional to the voltage across the two point under constant temperature and pressure. Shadder98 (talk) 16:57, 28 June 2021 (UTC)[reply]

 Not done: it's not clear what changes you want to be made. Please mention the specific changes in a "change X to Y" format and provide a reliable source if appropriate. ScottishFinnishRadish (talk) 20:49, 28 June 2021 (UTC)[reply]

The article states Ohm's law as an equation between numerical values, imposing a priori that V is expressed in volt, I in ampere and R in ohm. Presenting Ohm's law as an equation between dimensioned quantities has many advantages, such as properly supporting dimensional analysis. Boute (talk) 08:44, 24 October 2021 (UTC)[reply]

Reading this article, I came across the statement in footnote 12 "a professor who preached heresies was unworthy to teach science". Although the statement makes sense, and is used in multiple sources (which all refer back to several, often not anymore reachable originals), there is one slight flaw: The fact that the German State was not yet founded in the early 19th century, which is when this comment was supposed to have been made. I would assume that Prussia or some other state is meant, I was not able to find which one it was... Unless the original source can be found and correction can be made, I would recommend deleting the quotation. --Ohligse (talk) 16:56, 17 March 2022 (UTC)[reply]

The original source can be viewed here. Since it is a print book, it is not very relevant that links have gone dead, it can always be read in libraries. The source does not actually say German Minister of Education, it only says "Minister of Education". Since this statement caused Ohm to resign from Cologne University, and (I think) Cologne was within the territory of Prussia at the time, your surmise is probably right that this was the Prussian minister. But I don't think we should put that guess in the article – it could also have been a provincial government minister. SpinningSpark 18:02, 17 March 2022 (UTC)[reply]

This source correctly identifies the person as the Prussian minister. SpinningSpark 13:06, 25 June 2022 (UTC)[reply]

I removed the units from "where I is the current through the conductor in units of amperes, V is the voltage measured across the conductor in units of volts, and R is the resistance of the conductor in units of ohms." Ohm's law is independent of units, as it is a relation between quantities and does not include any unit-dependent numbers. The simplified statement is "where I is the current through the the conductor, V is the voltage measured across the conductor, and R is the resistance of the conductor." The original statement is misleading in that it implies the law would be stated differently if different units were used, which it would not. (Before anyone asks, yes, there are other units for voltage, current, and resistance.)Joe Avins (talk) 14:40, 21 June 2022 (UTC)[reply]

@Jqavins: That is not strictly true. Those of us old enough to have had to deal with the imperial units in our education will know that Newton's second law is not F=ma in the FPS system using standard units. Rather, it is a proportionality with a dimensional constant. It can be made an equality, but only by using non-standard units for either force (the poundal) or mass (the slug). Similarly, if one were to choose the Siemens mercury unit as the unit of resistance, Ohm's law would require a dimensional constant or else have to be stated as a proportionality. It is only an equality if a rationalised system of units is used. SpinningSpark 12:20, 25 June 2022 (UTC)[reply]

I see where you're coming from, but I beg to differ. A current of one amp passing through a resistance of one Siemens mercury unit would be a voltage. It would not be one volt, it would not be one of any named unit (as far as I know) but that's not important as far as the physics goes (though it would be damned inconvenient for engineering). In other words, to do computations using amps, volts, and Siemens mercury units would require an extra factor, but that sort of thing is exactly the reason not to specify units in a statement of Ohm's law (or Newton's third law for that matter). V (volts) ≈ 0.953 × I (amps) × R (Siemens mercury). But voltage, the quantity rather than the number, is always current times resistance, the quantities not the numbers. Force is always mass times acceleration, and extra factors of g are only needed because the unit called pounds had an identity crisis due to actually being two different units with the same name.

• Incidentally, in years past and again a week ago I have searched high and low for obsolete or archaic electrical units and never found any except the CGS units. So thanks for pointing me to this one. Joe Avins (talk) 18:28, 28 June 2022 (UTC)[reply]

You are talking yourself in knots here. Voltage is the quantity measured in volts, not the product . A potential difference unit that was rationalised with the Siemens mercury unit would not be "inconvenient for engineering". That would have been a perfectly rational system and voltmeters would be calibrated accordingly. Engineers did not go down that path because they wanted the volt defined in terms of the battery cells used in telegraphy (the principle use of electrical engineering at the time). Later, the volt was defined in terms of the heat produced in an electrical circuit. Newton's second law does not have an "extra factor" because the pound has an "identity crisis". It is because the units are not rationalised. The need for a constant was present in the metric system as well prior to the introduction of SI units. If you look in any pre-1960s textbook, the second law is always given as a proportionality (eg [7]) rather than an equality. This is quite generally true of physical laws – a constant of proportionality is always involved except where the units of measurement are chosen to make it unity. To see this, consider Coulomb's law which even under the SI system, the dimensional constant has not been rationalised out of existence. It can be eliminated by going to some form of natural units, but that does not mean that we should always write Coulomb's law without the constant.

I'm not arguing for units to be put back in the equation, but it has to be understood that there is a hidden assumption here that SI units are being used. That is not an unreasonable assumption today, but nevertheless, it is an assumption. SpinningSpark 07:32, 29 June 2022 (UTC)[reply]

While I agree with the discussion of what the true meaning of Ohms law is, one should consider the average reader: they’re looking for an understandable explanation of what Ohm’s law is. The simplest explanation is that ohms law states that the current (I) in a conductor with resistance R is equal to the applied voltage (V) divided by the resistance.

At this point getting into what was actually defined by Ohm is great, but I believe in the “KISS” approach in the first paragraph. tbitson (talk) 23:56, 14 November 2022 (UTC)[reply]

I've reverted this. I don't agree that cluttering the introductory sentence with symbols makes the statement of Ohm's law any clearer. It is also repeating what is already said after the symbolic expression is introduced. Also, "voltage across a conductor" is confusing and fairly meaningless, if not wrong. Across what? Where do I put my meter probes? One can have voltage across a pair of conductors, or a voltage across two points on the same conductor, but not a voltage on one conductor unless a reference point is defined. SpinningSpark 14:10, 15 November 2022 (UTC)[reply]

Aiming for simplicity is a valid thing to do unless doing so introduces error. Making an idea easier to learn by leaving out aspects that constrain it to be true is worse than pointless. Calling the equation V = IR Ohm's Law is a ridiculous mistake, even if it is so widely entrenched. Ohm's Law is the assertion that resistance is constant, meaning that current remains in constant proportion to voltage; V = IR is nothing more than the relation defining resistance, and applies whether a characteristic curve is linear or not! Saying that Ohm's Law states that current is equal to voltage divided by the resistance is just plain wrong, since that relation applies to all materials, whether they satisfy Ohm's (readily breakable) "Law" or not. Aboctok (talk) 23:55, 15 May 2024 (UTC)[reply]

Resistance is opposing current

All conductors show some opposition to electric current, this opposition to current is called resistance. There are several factors that affect the resistance of a conductor:

Material Length of conductor used Thickness of conductor used Heat or Cold

The 2 main ways of increasing the amperage in an electrical circuit are by increasing the voltage or by decreasing the resistance.

If you increase the components voltage across it, there will be more current flowing in the component (Too high of a voltage can cause the circuit to break)

If you increase the number of components in a series circuit there will be less current, therefore leading to an increase in opposing current (resistance)

The relationship between current, the power(voltage) and opposing current is called Ohm's Law ( I = V / R ). Where “R” is equal to the opposing current, calculated by ohms, “I” meaning the current calculated by Amps and the power which is voltage calculated by volts or “V”.

A change in the heat or coldness of a mineral will cause a change in the opposing current in the circuit. These materials are known as “non ohmic conductors” 2A00:23C5:E420:F401:EFC8:1DE4:442E:9247 (talk) 20:38, 30 January 2024 (UTC)[reply]

This edit request is likely to be denied since you have not specified what it should replace or where it should go in the article per the template immediately above. Moreover, almost all of what you have said is already expressed in detail in the article. —BillC ^talk 00:55, 31 January 2024 (UTC)[reply]

 Not done: it's not clear what changes you want to be made. Please mention the specific changes in a "change X to Y" format and provide a reliable source if appropriate. M.Bitton (talk) 16:31, 31 January 2024 (UTC)[reply]