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Physics for all[edit]

This is a humble request to all those super smart people that wrote the latest definitions of voltage (or any other physical quantity) on Wikipedia. I would love to see those old and incorrect definitions, if you know them. Why? because they reflect the history of the physical quantity, and thus have a more tangible meaning. This allows people to understand science with their "guts" and not with equations. If an old definition is 1% incorrect, that is OK, because probably 99% of the readers will understand it. At the end of the definition there could be a comment on how inaccurate that definition is. This would allow the readers to decide by them selves if that old definition is good enough for the "world" they live in, or if they should keep reading to understand a more accurate modern definition. P.S.: If you think there is a better place to post this suggestion, please do it. Carlitoscox (talk) 19:50, 27 January 2010 (UTC)

No, you are mistaken here. It is actually impossible to understand things as fundamental as voltage, electric current, resistance, momentum, magnetic fields, capacitance, inductance, power, energy, force, and acceleration without using mathematics and equations. There simply is no way, and it doesn't matter what your "guts" tell you. Just as Euclid told an ancient king in Greece: "There is no royal road to geometry." The only way to learn these concepts and their relationships is to use equations.
Almost all of the "numberless" definitions of the physical quantities mentioned above cause a lot more deception and condusion than they are worth. You just have to roll up you sleeves, get a sharp pencil and a lot of paper, and a calculator or a slide rule, and get to work learning about them. Do not deceive yourself! (talk) 00:46, 19 March 2010 (UTC)
The mathematical equations necessary to the efficient application of knowledge of the physical world do not underpin physical reality, but merely reflect it; nor did they spring, fully-formed, into the minds of their inventors; they are formalised statements of mental models that were developed as a result of careful observation and inspiration. While you may have a true understanding of your chosen fields, the attitude you express goes a long way to explaining some of my academic peers and "betters" who couldn't answer even some basic questions, except to rattle off a memorised formula or algorithm. Once I had gained my own understanding of those subjects, I quickly realised that these people actually had no true understanding of their own. Even Euclid begins his Elements with a series of definitions, given in common terms, and then builds upon these definitions to lay out his more complicated definitions and propositions. And that is a work of mathematics alone! There may be no royal road, but that does not mean that the road must be elevated above its surroundings, and begin with a climb up a vertical wall. In fact, by reducing all discussion on the topic to refined mathematical models, without "beginning at the beginning", as it were, it is you who seeks to build a royal road to physics. (talk) 02:05, 23 June 2010 (UTC)
Michael Faraday himself had no formal mathematical training, commanding only elementary skills in algebra and geometry. However, he arguably had a firmer grasp over the physical concepts of electromagnetism than any of his contemporaries. His "guts" led him to revolutionary discoveries in the field, not the least of which included classical field theory. Indeed, as Maxwell's Equations had yet to be derived, the laws of electromagnetism could not have been learned through mathematics alone (though many tried). The equations came later! Electromagnetism is a field in which simple laws interact in exceptionally complicated ways, and when that happens, there is nothing more useful than an intuitive grasp of the science. Faraday's mathematically-trained colleagues were unable to imagine how field lines could interact to produce the phenomena that he managed to predict and explain easily. Using mathematics alone can lead one to nonphysical theories. The physical concepts do indeed exist outside of mathematics, and math is merely a sufficiently flexible tool to describe them.--JB Gnome (talk) 06:49, 16 November 2010 (UTC)

Voltage IS NOT potential difference[edit]

Voltage can only be expressed as potential difference if there is no change in magnetic flux. If there is a change in magnetic flux, along a closed loop there is a voltage>0 - this would be obviously impossible if voltage was potential difference. Please have a look at Electromagnetic induction, what is called EMF there is voltage or electrical tension.

Oh, yes it is. I recently read in New Scientist, an article about memresistors, that the definition of voltage is the change in magnetic flux over time (dØ/dt). I've never seen that before. I do not doubt that a change in magnetic flux will cause a force on charges, hence a voltage, but the formula (definition) given also hints that any voltage implies a change in magnetic flux over time. I believe that's just wrong (i.e. imagine an ideal battery in a room with infinitive R - there is no change in flux. And even if R is less than infinity, the change in flux really depends on the capacity of the battery, not the voltage). I'm confused. In any case, this article should be mentioning magnetic flux more than it does. tobixen (talk) 01:34, 28 November 2009 (UTC)
No, electric fields and voltages are very fundamental in their nature, and they can readily by expressed in terms of electric charges, distances, etc., with no reference at all to magnetic fields. NONE
Once this is done, then by using Einstein's Special Theory of Relativity, everything in magnetism can be explained in terms of electric fields, voltages, and velocities. Thus, you need to learn as much as you can about voltages and electric fields, and then you can learn about magnetism later on. (After you have also studied the Special Theory of Relativity. (talk) 00:54, 19 March 2010 (UTC)
Agreed. It's not proper to define voltage as the time-derivative of anything, because voltage is still useful in purely static problems, where time derivatives would be zero.--JB Gnome (talk) 06:54, 16 November 2010 (UTC)

There is no discussion of changes in magnetic flux without first considering the voltage potential which causes electric current, which causes magnetic fields.[1], [2],[3]. In description it uses an incorrect analogy "In this case the voltage between two bodies is the thermodynamic work required to move a unit of charge between them." But it is that voltage itself which is the cause of the thermodynamic energy.[4]

We just need to stop ignoring those electrical currents and pretending it's moving charges.

"Although current is flowing through the capacitor, no actual charge is transported through the vacuum between its plates. Nonetheless, a magnetic field exists between the plates as though a current were present there as well. The explanation is that a displacement current ID "flows" in the vacuum, and this current produces the magnetic field in the region between the plates according to Ampère's law:...

...The magnetic field between the plates is the same as that outside the plates, so the displacement current must be the same as the conduction current in the wires, that is, I_D = I, which extends the notion of current beyond a mere transport of charge."[5]

So why are we not extending our notion of current????Steven J White (talk) 19:39, 5 June 2015 (UTC)


Electric tension[edit]

I think voltage should be replaced with electric tension. "Voltage" is an, in my opinion, an unnecessary link to one specific unit of measurement. The electric tension stays the same, no matter if you measure it in Volts, Statvolts or other units you could think up, like the quite absurd btu/elementary charge (). What do you call the electric tension of a powerline? Kilovoltage? You don't call a length "footage" or "inchage", do you? Ospalh 15:17, 17 May 2007 (UTC)

The rules for naming units of natural quantities recommend to avoid the naming of a quantity through a particular unit of measure of that quantity. Still, it is used frequently because is shorter than the name electric tension.-- (talk) 14:29, 5 February 2011 (UTC)
You are correct on all accounts, sir, and, in fact, English is the ONLY language that I know of that has this silly phenomenom (it's akin to substituting 'temperature' for 'farenheightage'), but it exists nonetheless, even in academia, it's a feature of the language, so Wikipedia should reflect that. —Preceding unsigned comment added by (talk) 12:56, 22 March 2010 (UTC)
Voltage is not an unnecessary link to one specific unit of measurement. The terms voltage and Volt both refer to the physicist Alessandro Volta. Similarly, the term "Newtonian mechanics" does not refer to one specific unit of force, the Newton. Both terms refer to an influential scientist in that field.Alhead (talk) 22:00, 11 July 2008 (UTC)
Sorry, fixed a link.Alhead (talk) 22:01, 11 July 2008 (UTC)
I doubt your analogy. Voltage is named after the unit, not after the physicist. Note how "Newtonian mechanics" isn't known as "Newtonage". OED shares my view, deriving voltage directly from Volt, not from Volta. dab (𒁳) 17:26, 2 September 2008 (UTC)
By this analogy the electric current should be called amperage.-- (talk) 12:44, 20 March 2011 (UTC)
I'll accept that the term came from the unit, not the physicist; I guess I just assumed otherwise. However, regardless of Ospalh's opinion on the subject, the term "voltage" is used colloquially as well as in text books, engineering classes, and elsewhere. The electric tension of a power line would not Kilovoltage, it would be a voltage of 110 kilovolts. Similarly, you say it would be a voltage of 1.67043664 E-17 btu/elementary charge. Perhaps it is an unnecessary link to one specific unit, but since the link exists, Wikipedia should reflect that. (talk) 22:00, 1 December 2008 (UTC)

I believe that the original query came from someone who just wants to quibble about terminology. He wrote, with the bolding removed:
I think voltage should be replaced with electric tension. "Voltage" is an, in my opinion, an unnecessary link to one specific unit of measurement.
What he should have written:
I think that the word "voltage" should be replaced with the word "electric tension". There is a big difference, because this statement is merely a statement about terminology.
As he wrote it to begin with, the way to read it is that, with the extra words inserted in brackets:
I think that [the concept of] voltage should be replaced with [the concept of] electric tension.
This is a much more serious matter: someone wants to completely discard the concept of "voltage" and to replace it with something else. This is very "heavy" - and also I will argue against this notion until Hell freezes over. It is lunacy.01:06, 19 March 2010 (UTC)

If the names "voltage" and "electric tension" are equivalent (corresponding to the same concept) then there is no conceptual difference between the two names.-- (talk) 13:29, 5 February 2011 (UTC)

Bad redirect[edit]

This redirect page has a history of pointing to different things:

None of these is satisfactory, because voltage is an electric potential diffrence, which is measured in volts. The article Volt is, in fact, mostly about voltage, which is an unacceptable confusion. Voltage should be its own article. Melchoir 11:42, 15 February 2006 (UTC)

Volt is the unit that represents Voltage, there is no need to merge these articles. Captain scarlet 00:44, 18 February 2006 (UTC)
Electric current and Ampere,
Electric charge and Coulomb,
Electric power and Watt,
Electrical resistance and Ohm (unit),
Electrical conductance and Siemens (unit),
Capacitance and Farad,
Inductance and Henry (inductance),
Magnetic field and Tesla (unit)...
all have separate articles, and that's just in electricity. Electric field doesn't have an article on its unit, but presumably that's because the unit doesn't have a name. I'm sure I don't have to quote articles from other fields. Melchoir 01:21, 18 February 2006 (UTC)
No you don't, it is a good thing that all this units have their own article. In many cases I have linked an article to volt and it is to Volt that the links are clearly intended to link to, not voltage. Captain scarlet 13:45, 19 February 2006 (UTC)
I'm sorry, I may have misunderstood you... do you agree with my very first comment? Melchoir 22:18, 19 February 2006 (UTC)
Voltage does not reflect "the potetial difference" or "the current driving force" and hence is not a really good name. In non-English-speaking countries (e.g. France/Germany/Scandinavia) the word that translates to Tention denoted U is measured in Volts [V]. The French (who should know the SI) call it La tension électrique or just tension for short. --Oy5tein 14:57, 24 February 2006 (UTC)
I agree that "tension" is a more evocative name than "voltage", and the article Tension does note that it's sometimes used in English. But according to Wikipedia:Naming conventions (common names), we should use the most common English name for the article, and that is "voltage". The information about other languages is interesting, and it should go into the article when we create it. Melchoir 20:29, 24 February 2006 (UTC)
I concur to keep articles on the physics, i.e. voltage/potential difference/etc., separate from articles on the units in which they are measured. In voltage, simply state that in the SI voltage has the unit volt and reduce the article on volt (and other units) to the origin of their names, when it was adopted into the unit system, present definition and realisation etc. and maybe relation to other units. Dalle 15:48, 16 March 2006 (UTC)
The correct technical term is Potential difference. Voltage is informal language. 23:57, 6 October 2006 (UTC)

Electromotive force (emf) also needs to be considered. I agree that the quantities being measured should be separated from their units, and that the one thing voltage should not redirect to is volt. Gene Nygaard 16:16, 30 March 2006 (UTC)

Yes, but voltage should redirect to the correct term potential difference. 00:03, 7 October 2006 (UTC)
You are just quibbling about terminology here.
Also, the writer above is correct who stated that there is not a (named) unit for electric fields in the way that there is for magnetic fields. The standard unit for electic field it the volt per meter, or volt/meter. (talk) 01:17, 19 March 2010 (UTC)


Okay, I've split this article from Volt. English Wikipedia is now roughly the 25th language to have separate articles on volts and voltage. I find it interesting that of all the interlang links I've found, none of them are apparently named "Voltage", in stark contrast with the interlang situation at Volt. Rather, most languages seem to call voltage "electric tension"; after finding a couple of English webpages on Google that recommend "electric tension" at English, I have made electric tension a new redirect to Voltage and added the phrase in bold to the top of the article.

Some of the interlang links, such as fr and ca, are technically not about electricity, but they launch into electricity almost immediately, so I've linked them; I think it's okay that those articles then link back to en:Tension or en:Potential difference. However, I'm going to go through the "electric tension" articles that currently link back to en:Potential difference and link them to en:Voltage instead. Melchoir 06:46, 9 April 2006 (UTC)

Equations for DC circuits[edit]

In the section on DC circuit equations, the following are listed:

Multiplying equations 2 and 3 produces , which contradicts with equation 1. I don't know enough physics to know if this is (somehow) right, or what would make it correct. However, I'm guessing that equation 1 is not correct, and will delete the 9.

(Comment largely copied from pre-split Volt)

Ealex292 06:52, 9 April 2006 (UTC)

Thanks for taking care of that! I guess I'll copy over more of the discussions at Talk:Volt that now belong here. Melchoir 07:06, 9 April 2006 (UTC)

linkato1 8:58, 5 March 2011 (UTC)

I'd furthermore like to change the symbol for potential, potential differenve and voltage throughout the wikipedia to U. V is for volume as may seen in the SI definition of measures.— Preceding unsigned comment added by Linkato1 (talkcontribs) 08:58, 6 March 2011 UTC

Please provide a citation to "SI definition of measures." Jc3s5h (talk) 13:09, 6 March 2011 (UTC)

Hydraulic analogy[edit]

The following is from Talk:Volt, since the material in question used to live at Volt:

Re: "water circulating in a network of pipes, driven by pumps in the absence of gravity, then the potential difference corresponds to the hydrostatic pressure difference between two points". The "hydrostatic pressure" hyperlink is redirected to "fluid pressure", perhaps because "hydrostatic pressure" is more narrowly, and I presume correctly, defined there as the pressure of a fluid due to the weight of the fluid, which makes the "absence of gravity" correspondence to "hydrostatic pressure" on the "Volt" page problematic. Perhaps the simple solution is to change the linked reference text from "hydrostatic pressure" to "fluid pressure"? I am new to both Wiki and physics, and perhaps there is more to this than I can see, but for anyone simply following the linked text, there is I think a problem. Oct 22, 2005

I changed to fluid pressure, as above. I also removed most of : "Voltage is a convenient way of quantifying the ability to do work without having to specify the amount of charge (the number of electrons or other particles) involved. This simplifies electrical calculations, where the number of particles that move is usually of no interest." I don't think it is helpful. The amount of charge might be relevant in talking about the voltage across a capacitor, but the voltage induced across a conductor by a changing magnetic field has nothing to do with quantity of charge.--agr 11:25, 2 December 2005 (UTC)

W/ some minor exceptions, this is a good discussion of voltage. However, there is nothing as to what voltage is rigorously. What is it about certain electrons that makes them different from others of lower/higher voltage?

Voltage is a property of an electric field, not individual electrons. See "Technical definition". An electron moving across a voltage difference gains energy, often measured in electron-volts.(hmmm maybe this belongs in the article) --agr 11:34, 2 December 2005 (UTC)

Melchoir 07:14, 9 April 2006 (UTC)

Ryan858 removed the statement that voltage is analogous to fluid pressure in the opening paragraph with the summary note that it was redundant. This may be mentioned in the main article but it is appropriate to expand on the opening paragraph in a article. Without it the opening paragraph is over-the-head of the average reader. I put the statement back. Rsduhamel (talk) 06:32, 12 March 2009 (UTC)


wouldn't it be more accurate to use ∆V instead of V?

It might be more suggestive, but it's not quite standard. Do you know of any texts that use ∆V to differentiate voltages from potentials? Melchoir 04:17, 29 April 2006 (UTC)
Its a rather sticky thing. A volt is a relative term, really. The difference between two points in it of itself. Confusingly, the electrical pressure of a point in space is of the unit 'volt'. But you can't just measure it. What do you compare it to? You compare it with another point in space, and that is the voltage, as I'm to understand. The comparison between the relative electrical pressures is voltage. ∆V is usually used to describe the change in voltage. That is, a change in the measurement that is between two points. You can easily say that the voltage of a battery has changed from when it was new to when you tossed it because it was drained. That's more of a ∆V. Disclaimer: I'm an EE, not a physicist, which is a big difference. Kevin_b_er 00:28, 2 June 2006 (UTC)
Use the term potential difference to describe the voltage between any 2 points! 8-)--Light current 00:38, 2 June 2006 (UTC)
There would potentially be confusion with Delta-v.—An Sealgair (talk) 02:32, 16 October 2009 (UTC)

Voltage with respect to a common point - that easy?[edit]

Is there a way to tell an absolute voltage value? I can imagine that there are problems specifing one single ground at least in moments when a power plant transmission line is supposed to be connected to an existing intercontinental electricity network. Or is ground everywhere the same on our planet? --Abdull 15:56, 12 December 2006 (UTC)

There is no such thing as an absolute voltage. Even if a "universal ground" could be established, it would just be a convenience, it wouldn't change the fact that all voltage measurements give the voltage of one point with respect to another. For this reason I object to the sentence "it is not usually practical to measure the absolute electric potential of a point" in the article, since an absolute electric potential fundamentally cannot exist. "Ground" is not the same everywhere, see Telluric current. Rotiro (talk) 06:13, 3 August 2011 (UTC)

An absolute voltage exists in theory at least and can be defined as the work required to move a test charge to that point from infinity. This is the approach adopted, for instance, when calculating the potential of electrons in an atom in the Bohr model. The practical difficulty of making such a measurement is an entirely different question. SpinningSpark 07:23, 7 August 2011 (UTC)
"From infinity"? In the universe we live in, there is no "infinity" that is arbitrarily far from all charges and fields. Wherever you go, there are always more galaxies. :-) Therefore I strongly agree with Rotiro, absolute electric potential does not exist, there's just various choices for the zero of potential and nothing in the world can declare one choice to be more correct than another. Even in textbooks, the "zero at infinity" definition is used in examples where it's a prudent definition, but then in other problems where "zero at infinity" doesn't work (e.g. the potential profile due to an infinite charged sheet), the zero of potential is defined to be somewhere else. I suppose you can say that the zero of potential is the potential in intergalactic voids, but #1 we don't know that the potential there is constant, #2 why should intergalactic voids have such a fundamental role in the theory of electricity? #3 it's a very impractical definition for us humans. :-) --Steve (talk) 15:36, 7 August 2011 (UTC)


File:Real Potential Difference Number 1.svg
Belgium, France, Netherlands, others ?

Real Potential Difference Number 2.svg
Czech Republic, Germany, others ?

Real Potential Difference Number 3.svg
USA, others ?

Other possibilities?

Tsi43318 16:05, 27 February 2007 (UTC)

Eduardo informatico[edit]

es una persona que trabaja en sistemas fondeur

¿OK, pero ella habla inglés? —Preceding unsigned comment added by (talk) 02:30, 23 June 2010 (UTC)


Under ways to measure voltage a potentiometer is given as one method... I realize that this coupled with other equipment can measure voltage, did they mean a galvanometer, coupled with a potentiometer? —Preceding unsigned comment added by (talk) 21:44, 27 January 2008 (UTC)

Merge from potential difference[edit]

Please comment at Talk:Potential difference#Merge about editing that article into this one. --Gerry Ashton (talk) 16:54, 20 April 2008 (UTC)

Is this correct?[edit]

A while back an IP edited "Specifically, Voltage is equal to energy per unit charge." into the first paragraph. Can anyone verify that it's correct and in the right place? —Preceding unsigned comment added by Ryan858 (talkcontribs) 03:57, 12 September 2008 (UTC)

Yes, it's correct. I added a footnote. --Gerry Ashton (talk) 04:24, 12 September 2008 (UTC)


The notation voltage from point A to B (VA-VB) seems to be against convention. While voltage is not a vector quantity it is the difference between two points. Where the equation is

The notation voltage from point A to B (VB-VA) fits with the convention of a quantity which is measured by the difference between two points, (final-initial). Similarly the equation can be reworked to

Is there any reason the current notation should be kept? —Preceding unsigned comment added by (talk) 21:24, 20 February 2010 (UTC)

Please provide a phrase we can search for in the article so we can tell exactly what point in the article you are concerned about. Jc3s5h (talk) 21:48, 20 February 2010 (UTC)
After a bit more reading, the equation is fine because it describes electron flow. I'm still concerned with lines 1-2 in the Definition section.


This article sucks. Will somebody fix it, please? I don't care about the details of surface effects. I don't even know what the units of voltage are. I just need to know what the difference is between a 9 volt and 12 volt battery are. —Preceding unsigned comment added by (talk) 15:29, 8 December 2009 (UTC)

The difference is 3 volts. But you're right, someone needlessly obfuscated this article. We could explain voltage like the physics textbooks do: start off with an imaginary unit charge in free space, it will feel a force on it due to a static electric field, the amount of work required to move that charge from point to point is the electric potential, then talk about the general case with time-varying fields. At this point we can drop in the "integration along a curve of the electric field", as if that actually explains anything. Then explain that in practical circuits with good conductors, the surface of each conductor is nearly at a constant voltage (equipotential surface, as if that explains anything), and we can measure voltage between any two conductors (it's still the path integral of the electric field between the conductors, of course, but we don't usually think of it that way and usually think of voltage as an attribute of the *conductor* and not of the *space between two conductors*).
All that "surface effects" and "chemical effects" stuff is a red herring anyway, since by definition these affect the electric field. None of that was referenced, either - and I don't imagine there was a very long period in which voltage was defined in anything but the modern way...the physics has been worked out for a very long time. Those 19th century cats named after the electrical units <! -- you know, the guys called Farad and Henry and Joule and Watt and Gramme and Volt and Amp and Erg and Metre...--> really knew where their towels were.
I'm not sure I understand this well enough to explain it clearly. But I've got some good textbooks.
I'd love to read a well-researched and coherent explaination of the system of electrical units, but Wikipedia doesn't have it yet...and I'd have to do a lot more reading before I could write it. It's much more fun *reading* a good article than *writing* one. --Wtshymanski (talk) 16:09, 11 March 2010 (UTC)
It's been my Wikipedia experience that any article that starts off by fussing about the difference between upright and italic symbols, SI vs non SI units, or other similar cat-lady-like babbling, is heading in the wrong direction. Simplify, man! No-one CARES about the mathematical notation till you get to the maths ( and then you can use whatever notation is convenient) - the maths notation doesn't explain the physics, no matter how many hours you spent poring over teh books to get it right on the final exam. --Wtshymanski (talk) 16:55, 11 March 2010 (UTC)


It's against Wikipedia policy to revert an edit more than 3 times in one day. --Wtshymanski (talk) 20:46, 19 April 2010 (UTC)

An arrogant , rude and bullish attitude with little else is not impressive.Wdl1961 (talk) 02:01, 20 April 2010 (UTC)

Note that 2 other editors joined Wtshymanski in removing your discussion of hydraulic analogs. I agree that it is off topic. The consensus is not to include it in this article. Please do not re-add it unless and until you can establish a consensus here that it belongs in this article. This is not at all a "3rr edit war" between two editors. Edison (talk) 15:02, 20 April 2010 (UTC)

Bad illustration[edit]

The article shows a digital multimeter set to AC voltage, with nothing connected to the leads, displaying 0.385 volts. It must be picking up some induced AC. A better illustration would show it with the leads shorted displaying 0 volts, or connected to a battery or outlet displaying some more meaningful voltage. Edison (talk) 21:14, 9 January 2011 (UTC)

We can't see where the leads run off. There's all sorts of reasons that the meter reads non-zero with the leads (apparently) disconnected, and thoughtful consideration of these reasons would be a rich and rewarding subject - though off-topic for this article. Scepticism about what a meter is apparently reading is not the least valuable lesson of a lifetime. --Wtshymanski (talk) 23:47, 9 January 2011 (UTC)
We see the ends of the leads not connected to anything. The present thread is fully on point in my attempt to improve the article by finding a less peculiar illustration. Edison (talk) 23:05, 14 January 2011 (UTC)

Time varying fields[edit]

On visiting the Hall of Ideal Physics Exhibits (bypassing the room with the massless pulleys, frictionless plane, and the ideal gases), we come to the exhibition of Voltage. Two shelves, one shelf connected to +V, the other from -V (supplied by the Ideal Voltage Source on the other side of the room). It's a hands-on exhibit, so you're invited to move the test charge +Q from the -V shelf to the +V shelf - groaning and struggling you put +QV joules of energy into the charge to accomplish the feat; and reversing the move yields -QV joules of noise and pinched fingers. But on Sundays the cleaning lady polishes the shelves. She's long since learned to disconnect the Ideal Voltage Source, and then it's no work at all to move the test charge. So, what is the potential difference? A time varying field gives non-unique results for potential. --Wtshymanski (talk) 20:10, 13 May 2011 (UTC)

W = Work done not Watts[edit]

Was anyone else initially taken off guard by this picture: ? It shows Work Done = W, which I thought was usually ascribed to watts. We could keep the 'W' if we added the SI units after, like: J/((q/s)/s) = J / q (where q is charge and therefore (q/s) = current). Thoughts? TFJamMan (talk) 16:17, 5 January 2012 (UTC)

Which letter is used is arbitrary and depends on which text book you're quoting; there's no need to match the letter with the units, else all the resistors on the diagram would be labelled in Greek letters. One could imagine a parallel universe where James Prescott Joule stayed a brewer, where computation is carried out by steam-driven brass gears, where the French revolution was successfully suppressed and electrical potential difference is measured in foot-lbs per Heaviside. What do the textbooks say? --Wtshymanski (talk) 17:21, 5 January 2012 (UTC)
W is indeed the abbreviation for the unit, watt – the unit of power. W (correctly in italics) is the common abbreviation for the quantity work. There are different abbreviations for units and physical quantities. For example, work is measured in the unit joules, abbreviation J. While the unit names and abbreviations are unambiguous the abbreviations for physical quantities are not. For example, P can mean power or pressure. Potential energy can be U or V or even PE. Using italics for quantities does help distinguish the two types of terminology. Dger (talk) 15:58, 12 April 2017 (UTC)

The article is crowded with nonsense[edit]

so I cannot understand why this talk page is discussing trivia. Take, for example:

"Voltage is defined so that negatively-charged objects are pulled towards higher voltages, while positively-charged objects are pulled towards lower voltages." ??? Something like that would be true for potentials, but when electric potential exists, voltage is merely a potential difference. And how can a greater difference pull anything in the opposite direction than a lower one!

And the preceeding sections on definition (including the lead) are full of loose babble. Until some informed editor undertakes to write a new article, I suggest that this one should be replaced by the voltage definition from the Electropedia, which is approved by the International Electrotechnical Commission (IEC).

In brief:

In the case of an irrotational electric field (i.e. a conservative field that can be described by potential gradient), the voltage is independent of the path and equal to the negative of the electric potential difference between two points. A common examle is an electrostatic field.

However, a time dependent magnetic field induces electric field curl (see e.g. the Maxwell equation describing Faraday law), and such field cannot be described by potential gradient. Therefore, in general, voltage is "a scalar quantity equal to the line integral of the electric field strength along a specific path linking two points".

And that is all there is (no babble about combining this and that). The equations could be added. (And then someone might discuss how magnetic forces are derived as relativistic effect of electrical forces, but that is not the usual approach in electrotechnics.) Note: The IEC voltage sign convention is not uneversally accepted.--Ilevanat (talk) 01:10, 10 February 2012 (UTC)

Tell your grandmother/spouse/neighbor at the next bar stool that voltage is "a scalar quantity equal to the line integral of the electric field strength along a specific path linking two points". Keep careful track of the dialog that results and see if the explanations you have to make are longer than the present article. We like mathy definitions of things because we feel scientific when we use them; that's why scientists take so much math. But you should be able to explain this to the proverbial barmaid. --Wtshymanski (talk) 02:51, 10 February 2012 (UTC)

Oh well, perhaps you can fool your barmaid by the present article statement: "Mathematically this is expressed as the line integral of the electric field and the time rate of change of magnetic field along that path." Because she is not expected to know that the effect of "the time rate of change of magnetic field" is already contained within the instantaneous electric field strength and, consequently, within "the line integral of the electric field".

My point was that the article should not contain such babble, nor the nonsense cited in the "for example" illustration above (even if the barmaids might be able to understand that more readily). And I suggested the Electropedia formal definition only as a temporary substitute, until somebody adds "the barmaid explanations" in a correct way.

There, however, that somebody might face some difficulties, especially if he tries to address not only barmaids, but also highschool and college students as well. I believe that voltage can be best explained as "the work that would be done by electric field" (on a unit charge), or the work against the field (if the opposite sign convention is adopted). Actually, I was lead here following the links from the work articles. Difficulties I mention are related to what I preceive as a rather messy exposition of the Work (physics) article (and an even worse and entirely unnecessary article on electrical work). For a while, I shall hang there, hoping some more people will join talk pages, so we can reach consensus about most appropriate edits. I would not feel comfortable explaining volatage through work before that (not to mention the fact that there should be many people better acquainted with electrotechics than I am).--Ilevanat (talk) 00:52, 11 February 2012 (UTC)

I like the "work done to move a test charge between two points" but is it general enough? --Wtshymanski (talk) 01:39, 12 February 2012 (UTC)
What do you mean? That's the standard textbook definition. Andy Dingley (talk) 09:08, 12 February 2012 (UTC)
That's what I thought. Dusting off my "Basic Electromagnetic Theory" by Paris and Hurd, they don't get around to defining "voltage" until page 544, and that's in a book that doesn't have any two facing pages without an integral sign or vector notation. P&H give the line integral and say it reduces to the definition of potential difference in the static case. Good enough for me. --Wtshymanski (talk) 16:50, 12 February 2012 (UTC)

Unfortunatelly, some facts in science can be stated both simply and accuratelly only when full mathematical formalism is used (and that is one of the major reasons it has been developed). Then comes the tricky part of explaining that in non-mathematical (or less-mathematical terms). In texbooks, such explanations are usually worked through and given in a certain context, and they do not necessarily have to be fully general, accurate and comprehensible when displayed as stand-alone statements. And even in the present Voltage article, there are a number of good and correct statements (and parts of statements); the problem is that they are sprinkled with babble and nonsenses that cannot be just simply erased to produce a coherent article.

The general and accurate definition can be reduced to: "Voltage is the line integral of the electric field along a path linking two points". Now, there comes the problem of reformulating this in terms of work.

The good thing is that "line integral of a force along a path linking two points" equals work of that force along that path. And a most reasonable straightforward implementation would be: "Voltage is equal to work of the electric field along a path linking two points".

But now "the bad things" and dilemmas follow. And that is why I did not simply re-write the article. (And if I did, I would have started the lead with this last definition, and then immidiately went to the static field and potential difference.)

The reader may not be aware, but the writer should be, that force does work acting on some object (in this case, a charge) while its applicaion point moves in time along that path. The force may change due to passage of time; the charge may affect the field. None of these unwanted eventualities appear in the "line integral of the electric field". So, there remains a whole story...--Ilevanat (talk) 22:55, 12 February 2012 (UTC)

"some facts in science can be stated both simply and accuratelly only when full mathematical formalism is used"
Feynman could do it without. Andy Dingley (talk) 00:39, 13 February 2012 (UTC)

I would not quite agree on that. But, regardless, any specific suggestion on how to use some of his statements (sometimes rather context-dependent, at least in his "Lectures") within this article, would be welcome.

I see now I did not comment on the "work done to move a test charge between two points". It is a familiar textbook statement. There, from the context, it must be clear what the phrase "test charge" means (if it is a good textbook). E.g. it is a unit charge (if the work is not divided by the charge) and it does not affect the field (by moving other charges) - that is why some authors prefer "small charge". It also must be clear that the voltage exists whether or not that work is actually done. To fix the sign convention, it might be discussed who moves the charge (the field or we against the field). What about time-varying field (it changes while we "move" the charge)? And where do we mention path-dependence in the non-conservative field? Only that much.--Ilevanat (talk) 01:17, 13 February 2012 (UTC)

Reader feedback: need mathmatical explanation[edit] posted this comment on 6 May 2013 (view all feedback).

need mathmatical explanation

Any thoughts?

Puffin Let's talk! 18:29, 6 May 2013 (UTC)

If some article should provide one, then it is electric field, not "voltage" itself. BTW, this problem is related to one old discussion on this page. Incnis Mrsi (talk) 19:04, 6 May 2013 (UTC)

Voltage is potential difference AND it is always from HIGH-to-LOW[edit]

There seems to be awful lot of confusion about many concepts of electrical phenomena, at almost every corner of the web we look at. The article on battery (and pretty much every other article on electrical phenomena) is a mess i think. They are absolutely great for me right now (and thanks a lot for that), but absolutely horrible for somebody who does NOT already know the concepts and NOT ready to leach details: s/he wont get the concepts, s/he won't get the details.

Electric potential is defined as the electric potential energy that a single charge-carrier particle of 'elementary charge' would possess at a certain location within an electric field. Therefore, electric potential is a property of a location (or point) that represents a certain distance away from the source-charge. In other words, electric potential is an attribute of different points within an electric field, not an attribute of objects carrying a net charge. In other words, a location (or point) within an electric field is said to have a high or low potential. So, why do we still use terms like "high potential terminal" or talk about "objects having a high or low potential"? BECAUSE an object that have a net charge represents the location (or point) of highest electric potential within its own electric field.

Voltage IS potential difference, i.e. difference between ELECTRIC POTENTIALS *at* TWO DIFFERENT NODES.

Voltage IS between TWO NODES (or POINTS) that are at different potentials.

Voltage is a relative concept, and thus there is NO voltage at a single node; When you say "voltage", you ARE talking about TWO NODES.

Negatively charged objects (i.e. objects that have a net negative charge) can NOT be "pulled towards higher voltages", BECAUSE this does NOT make sense. Negatively charged objects can be "pulled towards one END (or POINT) of a high voltage", BECAUSE a "voltage" has TWO ENDS and a net electric field between these ends. That's the definition of voltage: TWO ENDS and a net electric field between them.

Electric potential is a sign-sensitive, scalar quantity (V=k.Q/d) whose value is negative for a negative source-charge, whereas it is positive for a positive source-charge. Source-charge is the charge that creates the electric field within which electric potential decreases as the distance from the source-charge increases. A negatively charged object is pulled towards the positively charged END, and thus it is pulled towards the location (or point) of positive potential; for the sake of brevity, it is said that it is "pulled towards the positive potential".

What about terms "high potential" and "low potential"? Natural (Spontaneous) flow of a charge carrier particle is in the direction from high potential to low potential. It is the natural (spontaneous) direction of flow because no external force needs to be supplied for the motion to occur, which means the work is done by the nature, which means the potential energy of a charge carrier particle decreases as it moves in that direction. Since it is natural, it happens spontaneously; since it is spontaneous, it happens naturally.

Conventional current is THE current in which charge-carrier particles possess positive 'elementary charge'. Since charge-carrier particles are positively charged, they are pulled (naturally) towards the most negative potential. That's the "low potential terminal" for THE conventional current (or conventional flow).

As opposed to the conventional current, THE electron current is THE current in which charge-carrier particles are electrons, and thus they possess negative 'elementary charge'. Since charge-carrier particles are negatively charged, they are pulled (naturally) towards the most positive potential. That's the "low potential terminal" for THE electron current (or electron flow).

Consequently, when a certain type of charge (i.e. positive or negative) is said to be flowing from "high potential" to "low potential", THE high potential is high in terms of the type of flowing charge, i.e. for a positive flow (the conventional flow), positive terminal is "high", whereas for a negative flow (the electron flow), negative terminal is "high". In either case, natural (spontaneous) flow is FROM HIGH POTENTIAL TO LOW POTENTIAL, and the sign-sensitive, scalar expression of electric potential (V=k.Q/d) clearly says which direction (or location or point) is "high" for the type (positive or negative) of the flowing charge.

As for the BATTERY case: Charge-carriers inside the battery are NOT sub-atomic particles (e.g. electrons) like in the external circuit but they are ions in the electrolyte solution (or gel whatever). Therefore, for THE conventional current, charge-carriers inside the battery are cations (positively charged ions), whereas for THE electron current, charge carriers inside the battery are anions (negatively charged ions). And, AS ALWAYS, the natural (spontaneous) direction of flow is FROM HIGH POTENTIAL TO LOW POTENTIAL in terms of the type (cation or anion) of flowing charge: When THE electron current is considered, charge-carriers (anions) flow from the location (or point) where the concentration of anion is HIGH to the location (or point) where the concentration of anion is LOW. Now, high anion concentration is on the surface of cathode BECAUSE cathode is where reduction occurs, and anions are released/produced. Therefore, anions flow from cathode (positively charged electrode) to anode (negatively charged electrode). For THE electron flow, high anion concentration refers to low electric potential, and vice versa. That's why, inside a battery, sub-atomic charge-charriers (electrons or protons) flow FROM LOW electric POTENTIAL TO HIGH electric POTENTIAL, but charge-carriers (anions and cations) flow, as always, from HIGH POTENTIAL TO LOW POTENTIAL.

During RECHARGING a secondary cell (i.e. recharable voltage source), an external voltage source (or power supply) is connected to the emtpy battery in reverse bias, positive to positive and negative to negative, to overcome whatever voltage empty battery can put up and reverse the flow direction of charge-carriers (anions or cations) by reversing the redox equilibria on the surface of both electrodes.

As for the terminals of a common voltage source, whether electrostatic generators OR current-electricity generators: A charged conductor is a conductor that has a net charge (excess charge), i.e. the total number of electrons is NOT equal to the total number of protons.

Conductors allow an excess charge to "move freely" within the crystal structure, BECAUSE there are no energy gaps between filled and empty electron-energy-states, and thus charge has a place to go. Valence electrons in metals are referred to as "free electrons" because they are free-to-move to empty energy states, which happen to be ADJACENT to the valence energy states, with no energy gap in between.

Therefore, any excess charge is distributed to reach electrostatic equilibrium, at which the electrostatic force between every charge pair is EQUAL, and thus the excess charge is STATIONARY.

Electrostatic equilibrium *implies* that the net electric field within the conductor is zero, BECAUSE otherwise the charge experiences a net electrostatic force within the field and thus can NOT be stationary.

Gauss's law *implies* that the net charge of a conductor at electrostatic equilibrium is distributed over the SURFACE, leaving no net charge anywhere below the surface.

A conductor that has a net charge also has a certain electric potential energy whose source is the closely spaced charge-carrier particles that make up the net charge; when a net charge is accumulated on the conductor, charge-carrier particles are not separated from each other by infinities anymore, and thus they experience electrostatic repulsion from each other. This interaction between charge-carrier particles creates a certain electric potential energy within the conductor. — Preceding unsigned comment added by (talk) 14:22, 19 October 2013 (UTC)

Automobile Batteries[edit]

I have a nit to pick with this statement.

A common voltage for automobile batteries is 12 volts (DC).

I thought These were really 13.2 volts? Because each of the 6 cells is 2.2 volts. Is this worth changing? Jokem (talk) 02:31, 19 January 2015 (UTC)

I think it's worth changing. It's simply a question of accuracy right? You said you "thought" at they were really 13.2 volts. If you can find a source backing your claim up, I'd push forward with it! Chewbakadog (talk) 02:38, 19 January 2015 (UTC)
This link

- -says 2.1V for each cell, or 12.6 for a six cell battery. I don't think that is right. -My internet research seems to indicate 2.1v per cell, though. 2.2v is what I learned many years ago, so I wonder if something has changed since then or if I am remembering wrong. Jokem (talk) 08:51, 26 January 2015 (UTC)

Discussion about this article[edit]

Please note the earlier discussion of this article at Wikipedia talk:WikiProject Electrical engineering#Three articles, two concepts Oiyarbepsy (talk) 04:08, 21 May 2015 (UTC)

Voltage is really just potential energy?[edit]

"Voltage is electric potential energy per unit charge, measured in joules per coulomb."

Unfortunately our current definition reinforces an apparently-common misconception. Also, it misses a very important point about the nature of voltage.

Misconception: voltage is just potential energy, and without a test charge, there can be no voltage? Wrong. It's been wrong ever since Faraday and Maxwell defeated the obsolete "action at a distance" viewpoint. Yet here it is, 1820 physics concepts in all their glory, back again. Embarrassing!

Important point missed: voltage isn't energy/charge, instead it's actually a feature of the e-field. Ever since Faraday/Maxwell we consider E-fields and voltage to be real entities. They are not action-at-a-distance concepts created entirely by moving a test-charge. Yes, electric potential energy is created by moving a test charge, and the definition of potential energy can be done that way, but not the definition of voltage. Like other Potentials, gravity and magnetic, voltage exists in empty space even with no test-charge present. In an important sense, voltage *is the e-field*, in similar way that electric flux *is* the e-field. Flux and Potentials are two complementary ways to describe fields. With a field in space, flux lines are sketched in one direction, and Potential is sketched in perpendicular to the flux. Specifically, voltage is the set of equipotential surfaces of the e-field, while flux is vectors penetrating those surfaces perpendicular.

Is the following the definition of a (Classical) gravity field? "Gravity is potential energy per unit mass, measured in joules per kilogram." No it is not. That's an inside-out definition; it's the definition of potential energy being used backwards, to become the definition of gravity. We make the same mistake here with voltage.

Our equation-graphic with line-integral is correct. The text description should match it, or at least say something about it, and really need say nothing about potential energy.

Voltage is not potential energy, any more than gravity potential is really just the potential energy of a lifted weight. The g-potential existed in empty space above the ground, even before the weight was brought in. The voltage existed around a charged conductor before the test-charge was brought in. Wjbeaty (talk) 21:46, 18 October 2015 (UTC)

Well, Gravitational potential (rightly or wrongly) in fact is defined that way in Wikipedia: "In classical mechanics, the gravitational potential at a location is equal to the work (energy transferred) per unit mass that would be done by the force of gravity if an object were moved from its location in space to a fixed reference location." GliderMaven (talk) 23:19, 18 October 2015 (UTC)
Can you explain better how the units for voltage are in the form of joules, and the integral is a line integral of the force over distance, but that this isn't a potential energy thing?GliderMaven (talk) 23:19, 18 October 2015 (UTC)

Wikipedia is not an authority on the meaning of scientific terms nor is its mission to change the usage of scientific terms. It is rather a compendium of the ways the terms are used in reliable secondary sources. This is not the forum to advocate that certain terms stop being used in the way they are being used and that they be used in some other way.Constant314 (talk) 13:18, 20 October 2015 (UTC)
  • Semantics: If the word potential means that something could, maybe, happen in the future, then Voltage is not only potential energy, but also potential current and potential power. All you need is a source of Voltage, like, for examples, a battery, or a wall socket, then things can happen! (talk) 23:13, 20 July 2016 (UTC)

U as International Symbol: The International System of Units (SI) [8th edition, 2006; updated in 2014][edit]

legal international rules :

2.2.2 Table3 voltage — Preceding unsigned comment added by 2003:CC:93C1:7801:3D44:BA8D:E1AE:9BB (talk) 09:51, 23 June 2016 (UTC) electric potential difference, electromotive force unit volt V W/A

5. Writing unit symbols and names, and expressing the values of quantities

5.3.1. [...]Recommended names and symbols for quantities are listed in many standard references, such as the ISO Standard 31 Quantities and Units , the IUPAP SUNAMCO Red Book Symbols, Units and Nomenclature in Physics , and the IUPAC Green Book Quantities, Units and Symbols in Physical Chemistry [...]

5.3.2 Quantity symbols and unit symbols

[...]For example: The maximum electric potential difference is U max = 1000 V but not U = 1000 Vmax [...]

(no comment)--2003:CC:93C1:7801:ACE2:4354:B76B:104E (talk) 09:36, 23 June 2016 (UTC)

Transmission line voltage?[edit]

"The voltage in electric power transmission lines used to distribute electricity from power stations can be several hundred times greater than consumer voltages, typically 110 to 1200 kV (AC)."

Is it reasonable to state "typically to 1200kV" for transmission lines? "to 275kV" I would agree with (local standards may vary) and 400kV is used locally, but here it also says typically. 1200kV (even 400kV) is still very much the exception rather than the voltage atop a typical pylon that a reader might see. Andy Dingley (talk) 09:17, 11 April 2017 (UTC)

Average Voltage of AC[edit]

The average voltage of ac is under normal operating conditions near zero. What is really meant in the article is the voltage amplitude. That should be corrected. --16:42, 4 April 2018 (UTC) — Preceding unsigned comment added by TN (talkcontribs)