Talk:Voltage

Physics for all

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! 98.81.17.215 (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. 203.94.158.82 (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

Oh, yes it is. See below.98.81.17.215 (talk) 00:55, 19 March 2010 (UTC)

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.

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.98.81.17.215 (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.

Electric tension

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 ($1{\frac {\rm {btu}}{\rm {e}}}=6.5851046\times 10^{21}{\rm {V}}$). 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)

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 200.102.191.141 (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)

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. 129.7.202.125 (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)

Bad redirect

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

• Potential difference
• Electrical potential (Electric potential)
• Volt

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. 80.136.204.122 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. 80.136.204.122 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.98.81.17.215 (talk) 01:17, 19 March 2010 (UTC)

Split

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

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

$V={\sqrt {9PR}}$

$V={\frac {P}{I}}$

$V=IR\!\$

Multiplying equations 2 and 3 produces $V^{2}=PR$, 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)

Hydraulic analogy

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.

jauntymcd@sprint.ca 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)

Suggestion?

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?

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)

Real_Potential_Difference_Number

http://en.wikipedia.org/wiki/Real_number

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

Czech Republic, Germany, others ?

USA, others ?

Other possibilities?

Tsi43318 16:05, 27 February 2007 (UTC)

Eduardo informatico

es una persona que trabaja en sistemas fondeur

¿OK, pero ella habla inglés? —Preceding unsigned comment added by 203.94.158.82 (talk) 02:30, 23 June 2010 (UTC)

Error?

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 68.37.153.73 (talk) 21:44, 27 January 2008 (UTC)

Merge from potential difference

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?

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 (talk • contribs) 03:57, 12 September 2008 (UTC)

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

Notation

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

$(V_{\mathrm {A} }-V_{\mathrm {B} })=\;-({\mu }_{\mathrm {A} }-{\mu }_{\mathrm {B} })/e$

The notation voltage from point A to B (V_B-V_A) 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

$({\mu }_{\mathrm {B} }-{\mu }_{\mathrm {A} })/e$

Is there any reason the current notation should be kept? —Preceding unsigned comment added by 74.232.119.6 (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.

Comment

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 146.186.131.40 (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)

WP:3RR

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)