Talk:Electromotive force: Difference between revisions

Revision as of 05:28, 26 February 2006

Latest revision as of 15:03, 6 May 2025

(708 intermediate revisions by 69 users not shown)

Line 1:

{{Talk header|noarchive=yes|search=no}}

''Emf is often used as a synonym for potential difference, where the potential difference is induced by an energy source such as a battery. This usage is considered obsolete.''

{{WikiProject banner shell|class=B|vital=yes|

{{WikiProject Physics|importance=high}}

{{WikiProject Electrical engineering|importance=high}}

}}

{{Archive box|auto=yes|search=yes}}

== Use of this term is deprecated ==

I thought that it is not the same because of the internal resistance in the battery, and that therefore the concept of emf is still needed for a battery. - [[User:Patrick|Patrick]] 12:09 Feb 4, 2003 (UTC)

According to ISO 80000-6:2008 Quantities and Units - Part 6 Electromagnetism: The name “electromotive force“ with the abbreviation EMF and the symbol E is deprecated. See IEC 60050-131, item 131-12-22.

== What's obsolete? ==

== Electrochemical cell considerations ==

I believe the expression ''electromotive force'' in words is obsolete, but the expression ''emf'' in letters is not. The problem is the word ''force'' — an emf is not a force, so it should not be called one. Thus I recommend moving this article to '''EMF (voltage)''', and writing "The expression ''EMF'' used to stand for ''electromotive force'', but the term ''electromotive force'' is now obsolete, and ''EMF'' is a substitute for it."

:The electrical circuit through an electrochemical cell may be described as a series circuit of 5 ingredients. They are (1) The negative plate electronic resistance, (2) The negative plate emf value, (3) The electrolyte ion transport resistance factor, (4) The positive plate emf value, and (5) The positive plate electronic resistance. The functioning of the electrochemical conversion process is, of course affected by environmental factors, like temperature, and by electrochemical conversion inhibiting factors, like material depletion and/or passivation. and the design and construction of electrochemical cell has to minimize the detrimental effect of all these factors.[[User:WFPM|WFPM]] ([[User talk:WFPM|talk]]) 14:53, 1 September 2009 (UTC)

Any comments?

The Emf potential of the cells active electrochemical material is the quantitative measure of the level of an opposing voltage which would stop the electrochemical material's electrons from moving. Then if that voltage is lowered, the electrons will move through through the connecting circuit in the direction of the lower voltage potential. In rechargeable cells, an increase in back potential will reverse the electrochemical process and restore the electron supplying properties of the cell's negative and positive plate materials[[User:WFPM|WFPM]] ([[User talk:WFPM|talk]]) 19:42, 2 September 2009 (UTC)

[[User:Fg2|Fg2]] 06:20, Sep 5, 2004 (UTC)

== Introduction Should Include More Casual Language ==

:The term "electromotive force" is still used in the latest edition of Jackson's ''Classical Electrodynamics'', and a literature search of the last 14 years finds at least 250 journal articles that use the term in their titles and/or abstracts. So, I don't think there is any evidence to support the argument that the term is "obsolete" in the sense of "no longer used" or even "no longer used by professionals". Yes, it is a bit of a misnomer, but these things happen in language. [[User:Stevenj|—Steven G. Johnson]] 19:14, Sep 5, 2004 (UTC)

In the introductory section, before the table of contents, there should be 1-2 sentences

== Further editing ==

with language easily understood by a non-Physicist. That section could also include some disclaimer verbiage such as "approximately" or "like...". It would then go on to the more

I get confused with EMF -- is it the voltage based on the internal resistance of the cell, or is the sum total voltage which is required to support the circuit? Tanmay

precise introduction and explanation.

Altered the wording and also added a physical analogy for voltage as a force. Edit was done by me [[User:ElBarto|ElBarto]] as 203.79.121.174.

I certainly respect the current wording, and that using simpler language would be imprecise.

:EMF is not based on internal resistance. It is equal in magnitude and opposite in direction to the open circuit potential difference of a source.--[[User:Light current|Light current]] 20:58, 27 December 2005 (UTC)

But if you're not a real techie the current introduction is hard to read.

Something like:

The electrons flow out of the positive terminal into the negative terminal. This is because Ben Franklin guessed wrong when researching this. So as a convention (to stay consistent), we say electrons flow from positive. This is Pasive Sign Convention.

"EMF is an electrical property of devices like batteries and motors that is

:I don't think that's quite right. ''Current'' flows out of the positive terminal and into the negative terminal, but current was defined by Franklin as the direction that positive particles of electricity would flow, before anyone knew that it was actually the electrons, or negative particles, that flow in metal conductors, whereas the protons, or positive particles, are at fixed locations. So in fact, electrons flow out of the negative terminal and into the positive terminal, but since current is defined as positive charge flow, the direction of conventional current is just the opposite.

related to (similar to?) voltage.

There are several different technical definitions of emf.

Even the letters in the abbreviation "e m f" stand for different terms

in some textbooks. And the letter "F", which usually stands for "force",

doesn't mean the same thing as it usually does in Physics.

Although EMF can be measured in Volts, it doesn't have the same meaning as "voltage"

normally does in electronics.

The actual definitions of emf are rather technical."

My example above uses lots of vague words and is imprecise, so perhaps it's not up

:The mistake that Franklin made was not in choosing the direction of conventional current flow, it was in not understanding that it is ''negative'' charges that flow, whereas the positive charges are fixed in the solid structure of the metal. Of course, there was no way that he could have known at the time, since he lived and worked 100 years before Maxwell derived a complete theory of electromagnetism, 125 years before Thompson discovered the electron, and 150 years before Rutherford probed the structure of the atom and discovered the positively-charged nucleus.

to Wikipedia standards, so I'm posting it here instead.

Since it's in the introduction, and I think

it's clear that it's imprecise, wouldn't that make it OK?

Or perhaps somebody can do better while still be as clear?

[[User:Ttennebkram|Ttennebkram]] ([[User talk:Ttennebkram|talk]]) 07:27, 17 October 2009 (UTC)

:I don't think that's the way, but I did find a sourced "simple" definition to start with.

:But, in a twist of historical irony, Franklin's choice of showing current in the direction of positive electrical flow turned out, in the age of semiconductors, more correct than people often realize. In semiconductors, the total current results from the flow of both electrons and mobile ''holes'', which represent the absence of an electron in the crystal lattice and which behave just like positive particles of electricity. So the direction of current flow, which is the sum of the contributions from both electrons and holes, is the same direction as the flow of the holes, and opposite to the flow of the electrons.

:The lead sentence since [http://en.wikipedia.org/w/index.php?title=Electromotive_force&diff=298387212&oldid=prev this diff] (one of 28 Brews ohare edits of June 24, the day I had to take a break) says "emf is the external work expended per unit of charge to produce an electric potential difference across two open-circuited terminals." I'm not surprised you don't understand it, since it doesn't actually make any sense. And it's sourced to two documents that don't support it; the first says nothing about open-circuited terminals and the second is specifically about a closed loop. I think it doesn't actually take any work to maintain a voltage difference across open-circuited terminals, since no charge motion is required, so the work per unit charge to do that seems to be indeterminate. I know what he was trying to do, but the edit summary "''(Revision following discussion on Talk page; see Talk page for details)'' didn't exactly lead to an explanation of why this. When I came back and saw it I wrote on the talk page [http://en.wikipedia.org/w/index.php?title=Talk:Electromotive_force&diff=298493096&oldid=298389654 here] "So you punted on the opening definition, making it an open-circuit definition instead of the loop integral definition? Too hard to find a unifying definition?". But I guess I didn't see just how bad and unsupported it was, as I never did touch it. Time to try to fix it... [[User:Dicklyon|Dicklyon]] ([[User talk:Dicklyon|talk]]) 01:33, 18 October 2009 (UTC)

:We are actually very fortunate that Franklin made this "mistake" and defined current as flowing in the positive direction, because it makes electrical circuits much easier to understand than if he had chosen the opposite convention. It also eliminates the need for minus signs in all of the circuit equations and laws that govern electrical phenomena. The only hard part is to learn and remember that the direction of current flow is ''not'' the direction of electron flow, but rather the direction of positive charge flow.

The term "voltage" is introduced without definition in the lead-in, so that its relevance to emf is obscure. I lack the ability to rectify this. [[User:Mpulier|Myron]] ([[User talk:Mpulier|talk]]) 17:12, 19 June 2011 (UTC)

:-- [[User:Metacomet|Metacomet]] 17:24, 25 February 2006 (UTC)

== EMF or emf?Definition ==

Electromotive force: The driving force which maintains the flow of current in the circuit is called Electromotive force

Silly people who abbreviate things in lowercase. :-) mph, rms, emf. When will it end??

It is denoted by E. <span style="font-size: smaller;" class="autosigned">—Preceding [[Wikipedia:Signatures|unsigned]] comment added by [[Special:Contributions/202.56.7.148|202.56.7.148]] ([[User talk:202.56.7.148|talk]]) 10:23, 26 March 2010 (UTC)</span><!-- Template:UnsignedIP --> <!--Autosigned by SineBot-->

I know there's some convention for this, but it doesn't make sense to me. Is there anything in the manual of style about this? - [[User:Omegatron|Omegatron]] 15:38, August 9, 2005 (UTC)

The definition as given is patently absurd; a voltage cannot be defined as an energy. I have changed it to the quotient of energy & charge. A more radical criticism is this: as an engineer, I have no use for emf; it does not differ in any respect from any other voltage, and to suggest that it does can only be misleading and unhelpful to beginners. When a battery is connected to a resistor, the terminal voltages of the battery and of the resistor are absolutely identical and indistinguishable. It is absurd to call one a pd and the other an emf. The fact that one component is a source of energy, and the other a sink or load is a point of distinction between a battery and a resistor - that is between the two devices. It is not a distinction between 2 voltages or types of voltage. Whether a device acts as a source or a load can be distinguished by the direction of the current with respect to the voltage, not by any examination of the voltage alone. I feel that no discussion of "emf" can be complete without these points being made. The term is actually obsolete, and should be abandoned; we wisely make no similar distinction between types of forces. A further point is that in the article the "emf" of a cell is described as its open-circuit voltage, a series equivalent circuit being assumed. But whoever wrote this neglected the fact that a parallel equivalent circuit is equally valid, in which case the open-circuit "emf" would clearly be a "pd" - that is the voltage developed across the internal conductance by the internal current generator. [[User:G4oep|G4oep]] ([[User talk:G4oep|talk]]) 13:25, 30 January 2015 (UTC)

== Symbol ==

== First sentence ==

Moved here for Stevenj's talk page for a more general discussion: "Nothing, but there is no reason to put it in a large font. In any case, the most common symbol I've seen is a script \mathcal{E}, not a Roman-font E. —Steven G. Johnson".

The symbol I added ''is'' a script E, and the Unicode character for EMF. If it's showing up as a normal E, then it's something to do with the fonts you have installed on your computer. [[User:Porge|porges]] 04:40, 12 October 2005 (UTC)

...doesn't really make sense. Current is not defined as electrons and ions. Current is a flow of electric charge. The sentence is currently saying "that which tends to cause the flow of electrons to flow." The common saying that current "flows" is erroneous. Current does not flow. <small><span class="autosigned">—Preceding [[Wikipedia:Signatures|unsigned]] comment added by [[User:Pseudov00|Pseudov00]] ([[User talk:Pseudov00|talk]] • [[Special:Contributions/Pseudov00|contribs]]) 04:57, 11 April 2010 (UTC)</span></small><!-- Template:Unsigned --> <!--Autosigned by SineBot-->

== Can emf be measured directly? Or is it the pd you're measuring? ==

The "Electromotive Force" is that which enters a persons house through his electric power line connection, and causes activity in his connected and turned on electric appliances. Its intensity value is rated in volts and results in a flow of the electric current carrying constituents of the appliances. Its power or Energy rate delivery characteristic is rated in watts (joules/second), which value is integrated over a time period to arrive at the delivered energy value in Watt hours. Note that since the advent of AC power, there is practically no entry of matter through the power line connection into the house, Just the delivery of the electrical EMF and associated electrical power and energy.[[User:WFPM|WFPM]] ([[User talk:WFPM|talk]]) 18:28, 3 November 2011 (UTC)

Can emf be measured directly, or must it always be inferred from the pd presented at the terminals? If it must be inferred, when people are taught about measuring various emfs with a voltmeter or potentiometer etc., they are being given slightly the wrong story. Yes?--[[User:Light current|Light current]] 02:50, 26 December 2005 (UTC)

== what does this mean ? ==

Does nobody know the difference between emf and pd?--[[User:Light current|Light current]] 05:49, 25 February 2006 (UTC)

"For a time-varying magnetic flux linking a loop, the [[electric potential]] scalar field is not defined due to circulating electric vector field, but nevertheless an emf does work that can be measured as a virtual electric potential around that loop".

:I am not 100 percent sure, but I think the only difference is a negative sign, and the fact that emf is a bit anachronistic as a terminology. I am not sure why it is necessary or useful, and IMHO, it is easier to use the more precise and well-defined concepts of ''voltage'', ''potential difference'', and ''electric potential'' depending on the context. -- [[User:Metacomet|Metacomet]] 19:22, 25 February 2006 (UTC)

Unfortunately, many of the electromagnetic principles (ie Lenz law) use the term 'emf' but the people who discovered these principles could not have measured the emf they were talking about!--[[User:Light current|Light current]] 03:11, 26 February 2006 (UTC)

== Is this correct ? ==

::I am confused. What do you mean when you suggest the emf cannot be measured? Isn't emf simply the voltage that shows up on my portable multi-tester when I place it across two terminals (without electrocuting myself!)? Or actually, times -1 to change the sign? Or is emf more complicated than that? -- [[User:Metacomet|Metacomet]] 04:52, 26 February 2006 (UTC)

Youre measuring the opposing pd with your meter- not the actual emf (theyre the same value of course but opposite polarity) See my first post under this heading.--[[User:Light current|Light current]] 04:55, 26 February 2006 (UTC)

"In the case of an electrical generator, a time-varying magnetic field inside the generator creates an electric field via [[electromagnetic induction]], which in turn creates a voltage difference between the generator terminals. Charge separation takes place within the generator, with electrons flowing away from one terminal and toward the other, until, in the open-circuit case, sufficient electric field builds up to make further movement unfavorable. Again the emf is countered by the electrical voltage due to charge separation".

::And if I disconnect the two leads and connect them to the opposite terminals, my multitester will read the negative value of the pd, which is the... I am not trying to be difficult, but I just don't see any difference between emf and pd except for the minus sign, which is actually arbitrary in both cases anyway (since it depends on which way you decide to hook up the terminals, and which terminal you choose to call '+'. -- [[User:Metacomet|Metacomet]] 05:00, 26 February 2006 (UTC)

Fortunately, the answer is in the article:

<blockquote>

=== ''Distinction between emf and p.d.'' ===

In a DC machine the magnetic flux within the machine can be constant. What does "unfavourable" mean in this context ? Is not the open-circuit terminal voltage simply equal to the induced voltage ? Current does not flow because we are considering an open circuit, and not for any other reason.

''If an external circuit is not connected to a source of emf, an electric current cannot exist. Thus, between the terminals of the source, there must exist an electric field that exactly cancels the generated emf. The source of this field is the electric charges separated by the mechanism generating the emf. For example, the chemical reaction in the battery proceeds only to the point that the electric field between the separated charges is strong enough to stop the reaction. This electric field between the terminals of the battery creates an electric [[potential difference]] that can be measured with a voltmeter. The polarity of this measured pd is always '''opposite''' to that of the generated emf. The value of the emf for the battery (or other source) is the value of this 'open circuit' voltage. emf itself cannot be measured directly.''

</blockquote>

:--[[User:Light current|Light current]] 05:04, 26 February 2006 (UTC)

== External links modified ==

:I guess we will simply have to agree to disagree. If I connect the red wire of my voltmeter to the + terminal of a 9V battery, and the black wire to the the &ndash; terminal of the same battery, the meter will read +8.92 Volts. But if I then connect the red wire to the &ndash; terminal and the black wire to the + terminal, the meter reads &ndash; 8.92 Volts. So in one case, haven't I measured the pd, and in the other case the emf? -- [[User:Metacomet|Metacomet]] 05:20, 26 February 2006 (UTC)

Hello fellow Wikipedians,

Not so fast! ;-) If I were to say that emf is a ''cause'' and pd is an ''effect'', does that help any? You always need a source of emf in any circuit, but you can only measure its effect as a pd - yes?--[[User:Light current|Light current]] 05:23, 26 February 2006 (UTC)

I have just modified {{plural:1|one external link|1 external links}} on [[Electromotive force]]. Please take a moment to review [https://en.wikipedia.org/w/index.php?diff=prev&oldid=756141289 my edit]. If you have any questions, or need the bot to ignore the links, or the page altogether, please visit [[User:Cyberpower678/FaQs#InternetArchiveBot|this simple FaQ]] for additional information. I made the following changes:

==Maxwell's use of the term electromotive force==

*Added archive https://web.archive.org/web/20090320064922/http://ppp.unipv.it:80/Collana/Pages/Libri/Saggi/NuovaVoltiana_PDF/sei.pdf to http://ppp.unipv.it/Collana/Pages/Libri/Saggi/NuovaVoltiana_PDF/sei.pdf

:It is also interesting to note that, according to the WP article, [[James Clerk Maxwell|Maxwell]] used the term ''electromotive force'' to refer to what we would today call the ''[[electric field]]'', and not what we would call ''voltage'' or ''potential''. Since the electric field is defined as the ''force per unit charge'' acting at a point in space on a positive test charge, then Maxwell's is actually using the term ''force'' more or less in the correct sense. [[Electric potential]], on the other hand, is really nothing but ''[[potential energy]] per unit charge'', and so using the term electromotive force to represent potential energy is a bit of a misnomer. -- [[User:Metacomet|Metacomet]] 19:28, 25 February 2006 (UTC)

When you have finished reviewing my changes, please set the ''checked'' parameter below to '''true''' or '''failed''' to let others know (documentation at {{tlx|Sourcecheck}}).

:Note that in terms of units of measure, electric field is [[volts]] per [[meter]] or equivalently [[newtons]] per [[coulomb]]. And from the [[Lorentz force law]], we have:

{{sourcecheck|checked=false}}

::<math> \mathbf{E} = q\mathbf{F} </math>

Cheers.—[[User:InternetArchiveBot|'''<span style="color:darkgrey;font-family:monospace">InternetArchiveBot</span>''']] <span style="color:green;font-family:Rockwell">([[User talk:InternetArchiveBot|Report bug]])</span> 07:18, 22 December 2016 (UTC)

:So again, Maxwell's use of electromotive force to represent what we call the electric field makes good sense.

== Potential for a loop ==

:-- [[User:Metacomet|Metacomet]] 19:40, 25 February 2006 (UTC)

''For a time-varying magnetic flux linking a loop, the electric potential scalar field is not defined due to circulating electric vector field, but nevertheless an emf does work that can be measured as a virtual electric potential around that loop.[5]''

You can define a multi-valued potential for a loop of radius ''a'' using the angle:

<math> V = V_o \frac{\theta}{2 \pi} </math>

Then the electric field is

<math> E= - \nabla V = \frac{V_o}{2 \pi a} </math>

as expected.

== Variability of emf ==

The following statement in the article, just above the table of emf for various cells:

"The electromotive force produced by primary (single-use) and secondary (rechargeable) cells is usually of the order of a few volts. The figures quoted below are nominal, because emf varies according to the size of the load and the state of exhaustion of the cell."

is inexplicable. The statement that emf varies with load contradicts the definition of emf, which is potential difference in open circuit, when there is no load. Of course the voltage delivered varies with load. If the internal resistance is r and external resistance is R the cell with emf E will deliver current I = E/(R + r) and the delivered voltage is V = IR = ER/(R+r). V varies with R but E does not.

The statement that E varies with the state of discharge is experimentally correct but it is not explained in the section about the source of emf. This section presents a standard and simple model which predicts that E depends on atomic properties of the atoms and ions participating in the reaction. It is by measuring E that we determine these atomic properties. How can the results depend on the state of discharge of a cell?

[[User:Bukovets|Bukovets]] ([[User talk:Bukovets|talk]]) 16:59, 25 July 2017 (UTC)

== Capitalization ==

Should we go with the traditional [https://books.google.com/ngrams/graph?content=an+emf%2Can+EMF&year_start=1800&year_end=2008&corpus=15&smoothing=3&share=&direct_url=t1%3B%2Can%20emf%3B%2Cc0%3B.t1%3B%2Can%20EMF%3B%2Cc0 lowercase emf], or all-caps EMF? An anon capped, claiming "typo", I reverted back to the conventional lowercase, and he reverted back saying that "Common usage in this case is neither correct according to any of the manuals of style nor encyclopedic." But that's not true; most style guides do use lowercase emf (and older ones e.m.f.) according to [https://www.google.com/search?biw=1285&bih=635&tbm=bks&ei=sJzzWueXL4nw_wScmpWQCQ&q=emf+electromotive-force+intitle%3Astyle&oq=emf+electromotive-force+intitle%3Astyle&gs_l=psy-ab.3...10165.13793.0.14010.16.15.1.0.0.0.94.1041.15.15.0....0...1c.1.64.psy-ab..0.0.0....0.eiz6BE3VKJQ this book search]. [[User:Dicklyon|Dicklyon]] ([[User talk:Dicklyon|talk]]) 01:19, 10 May 2018 (UTC)

== Derivative as counterpart of integral. ==

The article provides

:<math>\mathcal{E}=\oint_{C} \boldsymbol{E} \cdot \mathrm{d} \boldsymbol{ \ell } </math>

showing the relation between emf and the ''integral'' of '''''E'''''. It seems logical that there could be an equivalent/analogous relation between '''''E''''' and the ''derivative'' of emf. If so, can it please be added to the article. <br>

—DIV ([[Special:Contributions/120.17.127.14|120.17.127.14]] ([[User talk:120.17.127.14|talk]]) 09:41, 9 August 2018 (UTC))

:Compare also

:<math> \nabla \times \mathbf{E} = -\frac{\partial\mathbf B}{\partial t}</math>

:from [[Maxwell's_equations#Macroscopic_formulation]] with

:<math>\mathcal{E} = -\frac{d\Phi_B}{dt} </math>

:from [[Faraday's_law_of_induction#Quantitative]].

:—DIV ([[Special:Contributions/120.17.127.14|120.17.127.14]] ([[User talk:120.17.127.14|talk]]) 10:18, 9 August 2018 (UTC))

== "emf" vs. "EMF" - inconsistent? ==

Why is it ''"emf"'' when it is ''"[[Counter-electromotive force|back EMF]]"''? (Or vice versa, why isn't it ''"back emf"''? --[[User:Mortense|Mortense]] ([[User talk:Mortense|talk]]) 22:59, 21 July 2019 (UTC)

:{{reply|Mortense}} As far as I know, "counter EMF" or "back EMF" is another name for "induced EMF", which is a particular type of EMF, due to electromagnetic induction. Does that answer your question? --[[User:Alej27|Alej27]] ([[User talk:Alej27|talk]]) 23:25, 29 January 2022 (UTC)

== The sign(s) in definition of emf ==

How come the sign in the definition of emf in a conservative electric field is different from the sign in the definition of the induced emf? [[Special:Contributions/2001:1470:FF80:5:5539:D087:2C3C:17CA|2001:1470:FF80:5:5539:D087:2C3C:17CA]] ([[User talk:2001:1470:FF80:5:5539:D087:2C3C:17CA|talk]]) 09:00, 23 December 2021 (UTC)

== Difference between voltage and voltage difference ==

Hi user {{u|Constant314}}. In the recent [https://en.wikipedia.org/w/index.php?title=Electromotive_force&oldid=prev&diff=1068710319 edit reversion] you said that voltage doesn't have to be a difference. As far as I know, it does. Voltage is also called electric potential '''difference''', not just electric potential; even [[Voltage|Wikipedia agrees]]. Don't you agree? If not, what does "voltage" mean to you? Are you saying that voltage is the same as electric potential? --[[User:Alej27|Alej27]] ([[User talk:Alej27|talk]]) 23:22, 29 January 2022 (UTC)

:Hello. Voltage is, unfortunately, a vague term that some people use as being equivalent to potential. However, if you want to replace "votage difference" with "potential difference", that would be fine with me. [[User:Constant314|Constant<b style="color: #1100cc;">''314''</b>]] ([[User talk:Constant314|talk]]) 23:33, 29 January 2022 (UTC)

::Good. I've changed it. I just noticed that this article, before my edit, suggested that voltage was potential difference, in the third paragraph of the lead section, where it reads "the equivalent emf can be measured as the open-circuit potential difference, or voltage, between the two terminals". --[[User:Alej27|Alej27]] ([[User talk:Alej27|talk]]) 02:45, 30 January 2022 (UTC)

== Electromotive force vs. source voltage ==

As has been noted in anonymous comment above, IEC/ISO has deprecated '"electromotive force" as the standardized term in favor of "source voltage" a few years ago ([https://www.electropedia.org/iev/iev.nsf/display?openform&ievref=131-12-22 IEC electropedia]). This should be acknowledged in the article in some way. --[[User:Jähmefyysikko|Jähmefyysikko]] ([[User talk:Jähmefyysikko|talk]]) 20:37, 27 February 2022 (UTC)

== EMF of emf ==

{{ping|Dicklyon}} We have had discussions across several articles in the past. Here is part of it [https://en.wikipedia.org/w/index.php?title=Wikipedia_talk:WikiProject_Physics&diff=next&oldid=1063932300 ]. Unfortunately, it doesn't show the conclusion. Here are the [https://books.google.com/ngrams/graph?content=emf%2CEMF&year_start=1800&year_end=2019&corpus=26&smoothing=3&direct_url=t1%3B%2Cemf%3B%2Cc0%3B.t1%3B%2CEMF%3B%2Cc0|"n-gram results" ] showing an overall perponderence of lower case, although recently that has reversed. Anyway the community consensus was to use lower case. So, I am reverting it back to lowercase, pending further discussion here. [[User:Constant314|Constant<b style="color: #1100cc;">''314''</b>]] ([[User talk:Constant314|talk]]) 15:33, 4 April 2022 (UTC)

:If you look into the books you'll see the EMF is usually for [[electromagnetic field]], and emf for [[electromotive force]], even recently. [[User:Dicklyon|Dicklyon]] ([[User talk:Dicklyon|talk]]) 16:24, 4 April 2022 (UTC)

== What is the proper ISO name? ==

The first subject on this talk page says "According to ISO 80000-6:2008 Quantities and Units - Part 6 Electromagnetism: The name “electromotive force“ with the abbreviation EMF and the symbol E is deprecated. See IEC 60050-131, item 131-12-22." In which case it seems to me that this page should be renamed to whatever ISO considers the proper term, and then [[Electromotive force]] should simply be a redirect to the properly-named page. EMF isn't a force, so probably shouldn't use the word "force" in it or emF.

But what is the proper name? When I look up "ISO 80000-6:2008 Quantities and Units - Part 6 Electromagnetism" or "IEC 60050-131" online the only results I get are for a book that I have to pay hundreds of dollars for. [[User:Em3rgent0rdr|Em3rgent0rdr]] ([[User talk:Em3rgent0rdr|talk]]) 19:18, 25 September 2022 (UTC)

:The standardized ISO/IEC names can be found from IEC's Electropedia. In this case [https://www.electropedia.org/iev/iev.nsf/display?openform&ievref=131-12-22 Entry 131-12-22]. The name is 'source voltage' or 'source tension'. --[[Special:Contributions/2A00:1398:4:9003:82E8:2CFF:FEEC:B393|2A00:1398:4:9003:82E8:2CFF:FEEC:B393]] ([[User talk:2A00:1398:4:9003:82E8:2CFF:FEEC:B393|talk]]) 08:09, 19 December 2022 (UTC)

:: The naming convention for pages on Wikipedia is [[WP:COMMONNAME]]. It is not [[WP:OFFICIALNAMES]] and it is certainly not IEC official names. Until the IEC deprecation of the term actually starts to become widespread, then there is no reason that Wikipedia should be bound by what they say. There are literally hundreds of books published in the 21st century still using it. I also find the IEC definition of ''source voltage'' troubling. For instance, the emf of an inductor is zero when there is no current flowing through it. So an inductor can never have an emf by that definition. Even national standards organisations such as [https://www.nist.gov/pml/special-publication-811/nist-guide-si-chapter-4-two-classes-si-units-and-si-prefixes NIST] and [https://knowledge.bsigroup.com/products/standard-guide-for-measuring-electromotive-force-emf-stability-of-base-metal-thermoelement-materials-with-time-in-air/standard BSI] have not yet felt obliged to purge the term from their publications. [[User:Spinningspark|<b style="background:#FAFAD2;color:#C08000">Spinning</b>]][[User talk:Spinningspark|<b style="color:#4840A0">Spark</b>]] 15:08, 19 December 2022 (UTC)

:: And why on earth are the IEC attempting to resurrect the old-fashioned term ''tension''. After all, [[Tension (physics)|tension]] is a force so has the same semantic problems as ''force''. [[User:Spinningspark|<b style="background:#FAFAD2;color:#C08000">Spinning</b>]][[User talk:Spinningspark|<b style="color:#4840A0">Spark</b>]] 15:15, 19 December 2022 (UTC)

== What is the analogy to water pressure? ==

Intro says:

> Sometimes an [[Hydraulic analogy|analogy]] to water [[Volt#Water-flow%20analogy|pressure]] is used to describe electromotive force.

But without explaining the analogy, that doesn't tell me anything useful (and actually adds confusion). When I look up the referenced citation for that (https://books.google.com/books?id=OW0SAAAAYAAJ&q=%22electromotive%20force%20is%20that%22&pg=PA172#v=snippet&q=%22electromotive%20force%20is%20that%22&f=false), I find two excerpts which do not really talk about pressure at all (but maybe there is other text outside of the excerpt that google books link provides which explains the analogy?)

My opinion is to delete that entire sentence because as it stands now it harms rather than helps understanding. Unless someone can provide a good simple clear explanation of the analogy. [[User:Em3rgent0rdr|Em3rgent0rdr]] ([[User talk:Em3rgent0rdr|talk]]) 19:28, 25 September 2022 (UTC)

:I see that "pressure" in that sentence is surprised hyperlinked to [[Volt#Water-flow_analogy]]. But even when clicking on that hyperlink it doesn't explain how emf fits into the analogy. I guess would be external energy applied per unit of water that increases pressure or something?? I still would say just delete that sentence if not providing a clear explanation. [[User:Em3rgent0rdr|Em3rgent0rdr]] ([[User talk:Em3rgent0rdr|talk]]) 18:41, 26 September 2022 (UTC)

::I think that the analogy is between EMF and pressure difference rather than pressure. For those who insist that EMF only applies to sources, it would be analogous to the outlet-inlet pressure difference at a pump (assuming incompressible water). [[User:Constant314|Constant<b style="color: #4400bb;">''314''</b>]] ([[User talk:Constant314|talk]]) 18:44, 26 September 2022 (UTC)

:::Ok. I'm thinking the analogy is really to the mechanical work of the pumping action on the water producing the change in pressure. I'm also noticing the word "analogy" was a suprise link to [[Hydraulic analogy]]...I would just write out the full name of the analogy. So maybe the sentence could be written along the lines of:

:::In the [[Hydraulic analogy|electronic–hydraulic analogy]], EMF is analogous to the [[mechanical work]] done by a pump on water that results in a [[Volt#Water-flow_analogy|change of water pressure (analogous to voltage)]].

:::I see that [[Hydraulic analogy|electronic–hydraulic analogy]] page does not actually mention EMF...maybe something could be added there. [[User:Em3rgent0rdr|Em3rgent0rdr]] ([[User talk:Em3rgent0rdr|talk]]) 19:17, 26 September 2022 (UTC)

::::Looks fine to me. [[User:Constant314|Constant<b style="color: #4400bb;">''314''</b>]] ([[User talk:Constant314|talk]]) 19:58, 26 September 2022 (UTC)

== Did Volta make a mistake? ==

Our article currently states {{xt|Volta's mistake of labeling it a "force" is a misnomer that persists as a historical relic}}. Calling Volta "mistaken" is a bit presumptious of us especially as the cited source describes this as neither a mistake nor a misnomer. It's hardly mistaken at a time when ''force'' did not have the firm definition it has now. We wouldn't call Isaac Newton's laws of motion "mistaken" and "misnomers" even though Newton's concept of ''force'' is at odds with what we now describe as force (Newton's force is what we now call ''impulse''). [[User:Spinningspark|<b style="background:#FAFAD2;color:#C08000">Spinning</b>]][[User talk:Spinningspark|<b style="color:#4840A0">Spark</b>]] 15:57, 4 November 2022 (UTC)

:oh good point. I've now edited to simply be:

:> However, electromotive force is not actually a force, but the label "force" persists as a historical relic. [[User:Em3rgent0rdr|Em3rgent0rdr]] ([[User talk:Em3rgent0rdr|talk]]) 17:24, 6 November 2022 (UTC)

::What you probably mean is "not considered a force according to a very narrow definition used by a small bunch of specialists." However, their jargon does not constrain the general use of the term ''force '' to include emf. [[User:Constant314|Constant<b style="color: #4400bb;">''314''</b>]] ([[User talk:Constant314|talk]]) 21:46, 6 November 2022 (UTC)

:::Not just that, but the units don't match up. Force in SI base units are 1 [[Kilogram|kg]]⋅[[Metre|m]]⋅[[Second|s]]⁻² while volt, the unit of emf, is [[Kilogram|kg]]⋅[[Metre|m]]²⋅[[Second|s]]⁻³⋅[[Ampere|A]]⁻¹, which differs by a factor of [[Metre|m]]⋅[[Second|s]]⁻¹⋅[[Ampere|A]]⁻¹.

:::And what is behind emf is not some separate force but rather the some type of actual force doing work.

:::EMF is more of an energy transfer to a circuit per unit of charge. [[User:Em3rgent0rdr|Em3rgent0rdr]] ([[User talk:Em3rgent0rdr|talk]]) 17:00, 7 November 2022 (UTC)

::::The units don't need to match up. Force of love. Force of nature. Force of facts. Military force. Police force. Delta force. Those are all legitimate uses of the word ''force''. It is just a general word for something that causes action. He named it ''electromotive force''. That is its name. No need to make an excuse because some other people came along later and specialized the term ''force''. [[User:Constant314|Constant<b style="color: #4400bb;">''314''</b>]] ([[User talk:Constant314|talk]]) 18:43, 7 November 2022 (UTC)

:::::This article is part of the electromagnetism wikipedia category which is part of physics, so this use of the word "force" in is specific to the physics term, so I do believe it is necessary to clarify that "electromotive force" is not a physical force. It is not making an excuse, but it is an important thing about the name that needs to be clarified for readers.

:::::[[:Category:Electromagnetism]]

:::::[[User:Em3rgent0rdr|Em3rgent0rdr]] ([[User talk:Em3rgent0rdr|talk]]) 19:18, 7 November 2022 (UTC)

::::::OK, but kindly leave out the stuff about "historical relic". [[User:Constant314|Constant<b style="color: #4400bb;">''314''</b>]] ([[User talk:Constant314|talk]]) 20:26, 7 November 2022 (UTC)

:::::::ok here is what I've shorten to now:

:::::::> This energy conversion is achieved by [[Force|physical forces]] applying [[Work (physics)|physical work]] on [[Electric charge|electric charges]]. However, electromotive force itself is not a physical force. [[User:Em3rgent0rdr|Em3rgent0rdr]] ([[User talk:Em3rgent0rdr|talk]]) 20:45, 7 November 2022 (UTC)