Talk:Electric current/Archive 2

Archive 1

Archive 2

Archive 3

Merged Electrical conduction

I merged Electrical conduction here. While the terms are not identical, the two articles had largely overlapping scopes, and their introductions did not make a particular distinction either. I think readers are better served with a single version. Should this article grow further (and it is not particularly long now), it can be split back but now using WP:SUMMARY style. No such user (talk) 10:20, 8 February 2011 (UTC)

Charge Defined Incorrectly

Q, or charge, equals the number of unit charges per volume, or cross sectional area times distance, of a conductor. It is not "the electric charge transferred through the surface over some time t." Page protected...could someone with the power and/or knowledge fix this. Thanks. Wolfworks (talk) 00:45, 31 May 2011 (UTC)

The whole sentence reads "The SI unit for measuring the rate of flow of electric charge is the ampere, which is charge flowing through some surface at the rate of one coulomb per second." What is wrong with it? It defines an ampere, not "charge". It could be more nicely formulated, but it is accurate as far as I can tell. No such user (talk) 06:21, 31 May 2011 (UTC)

In any case, Q is not equal to the number of unit charges per volume; that would be charge density. SpinningSpark 13:01, 31 May 2011 (UTC)

This is the talk page for current. Charge isn't defined here. What's wrong with the definition? Perhaps you're on the wrong page, and looking for Electric Charge rather than Current? See also the definition of Ampere. Current is coulombs/sec: quantity of charge per unit time which penetrates an imaginary plane (Gaussian surface), or more commonly, quantity of charge which passes one location on a wire per unit time. If you're talking about flowing charge/volume, then instead you're discussing current density, or charge flow per unit area per second. 128.95.172.173 (talk) 02:59, 1 June 2011 (UTC)

cathode/anode incorrectly labelled?

Contrary to the galvanic cell picture in the article showing the cathode as the electron/ion receiving lead of the circuit, I was under the impression that regardless of the nomenclature convention used to define current flow direction, the cathode is defined as the electron/ion doning lead and the anode as the electron/ion receiving lead. Please correct me if I am in error. (It is worth mentioning the example of the Cathode Ray Tube which is an example involving electrons.) —The preceding unsigned comment was added by Nargibay (talk • contribs) 01:46, 27 April 2007 (UTC).

You have it backwards. The cathode is where the electrons go in. With the cathode ray tube, you have to feed electrons into the cathode to replace the ones that it emits into the internal vacuum. In the galvanic cell, cations (+) from the electrolyte go to the cathode, making it positive, so it attracts electrons inwards from the external circuit. --Heron 17:36, 27 April 2007 (UTC)

In a cathode ray tube, the cathode is the electron emitter and the electrons are attracted towards the anode. In a galvanic cell, if you look at it from outside, things are reversed. The electrons go from the anode to the cathode. If you look at it from inside, the cathode is where + charges go to get an electron. In the case of a zinc-copper battery, the Cu(2+) charges go to the cathode and get 2 electrons, forming a coating of copper metal.

Vmelkon (talk) 05:42, 26 June 2011 (UTC)

Some tough questions about electricity

It's possible for the current to outrun the voltage in phase in some cases and vice versa right? Does this means that you can have for a brief moment (let's say 1 milisecond) a current which isn't supported by the voltage which is a basic requirement? I mean you cannot have current without having supporting voltage. Another problem is if the current has a speed of 300,000 km per second (like the light) and apply current to some conductor the moment the current starts to flow all the electrons in the given conductor start to move from the side with more negative atoms (-) to the side with fewer negative atoms (+) if we look at this process as pure chemistry/physics. The problem is electons don't have delay time. They are not like cars on a highway. The moment they move is the moment electric current is applied to the WHOLE CONDUCTOR no matter his lenght. All the electrons carry the electrical charge. So we end up with the theory that current doesn't have speed and don't depend on the difference of conductor's lenght. Another question is this. What happens if we have 300,000 km conductor and we apply voltage/current and after half a second the charge should reach 150,000 km of the conductor. If we stop the current what would happen with this charge if it cannot move any more? This question is connected with the previous about the speed of current.--Leonardo Da Vinci (talk) 11:24, 1 December 2010 (UTC)

The current is not observed over the entire conductor instantly. The step change in applied voltage will cause an electromagnetic wave to propagate down the length of the conductor, at close to the speed of light. So if you have a conducting pair that is 150,000 km long, it will take ~0.5 seconds before the electrons at the far end will begin to move.

Make that an EMF (Electromotive force) wave the moves down the line. and initiates the motion of the electrons in the direction of the field gradient. And then, in a resistive load, we get a buildup of voltage drop losses due to the accumulated individual losses of force due to the electron disassociation process.WFPM (talk) 21:12, 15 February 2012 (UTC)

Note also that it is possible for the phase of the current and the voltage to be different. This is due to the distributed inductance and capacitance of the cable. Oli Filth^{(talk|contribs)} 12:17, 1 December 2010 (UTC)

I am currently reading a book made by an electrician expert and he says this

"Low-frequency (50- to 60-Hz) AC is used in US (60 Hz) and European (50 Hz) households; it can be more dangerous than high-frequency AC and is 3 to 5 times more dangerous than DC of the same voltage and amperage.Low-frequency AC produces extended muscle contraction (tetany), which may freeze the hand to the current’s source, prolonging exposure. DC is most likely to cause a single convulsive contraction, which often forces the victim away from the current’s source."

yet I know exactly the opposite :). DC is deadlier in terms of same voltage/current because it is constant and not like AC alternating.--Leonardo Da Vinci (talk) 11:36, 3 June 2011 (UTC)

Intensité de Courant

The article starts out by explaining why we use I for current today. It comes from the French calling it intensité de courant and it comes from intensity. Another part of the article says "The letter I stands for the German word, "Intensität" meaning "Intensity"". What's up with that? Different people writing different parts of the same article? Vmelkon (talk) 06:05, 26 June 2011 (UTC)

As the editor who inserted the Symbol section of the article, sorry, I did not notice the mention of Germam "Intensität" later in the article when I did it. However, can I point out that that is entirely unsourced whereas my insertion is backed by four citations. SpinningSpark 14:57, 27 October 2011 (UTC)

Current flow

When we're talking about current flow we're usually talking about the moving of electrons and not about the movement of the atoms with which the electrons were associated. Accordingly, a copper (or aluminum) electric service line can serve to supply an electric service for a long period of time. A good way to observe this is to watch a welding procedure (reverse polarity), where the flow of electrons impacting the metal surface can be noted as a kind of wind appearance resulting in a heating and piling up of the material being welded.WFPM (talk) 20:43, 15 February 2012 (UTC) However, when Ben Franklin and others discussed the idea of current flow it was wrongly decided that the electrical current flowed from the plus terminal toward the negative terminal, which is backwards; so we are left with opposing theories about rules related to the effect of current flow phenomena.WFPM (talk) 20:52, 15 February 2012 (UTC)

(1) Current doesn't flow, charge flows. (2) Electric current (the flow of electric charge) is not identical with electron current (the flow of electrons). (3) In an electrolyte, e.g., inside a battery, positive ions flow in the direction of the electric current, negative ions flow in the opposite direction. (4) Ben Franklin and others weren't wrong. Sure, electrons flow from negative to positive in the external circuit but that is electron current, not electric current, a distinctly different concept. Alfred Centauri (talk) 02:29, 16 February 2012 (UTC)

Yes but within a battery cell the complete circuit involves 2 EMFs plus the 2 electron circuits within the cathode and anode grids, plus your positive ion flow through the electrolyte, and is accordingly considered to be an electron flow phenomenom.WFPM (talk) 17:24, 16 February 2012 (UTC)

It seems to me, at first blush, that the above is, at best, confused and, at worst, nonsense. Did you consider at all what I wrote? Current, electric current, is the flow of electric charge, not the flow of electric charge carriers. In other words, electric current (AKA "conventional current") is an abstraction. Alfred Centauri (talk) 01:32, 18 February 2012 (UTC)

When you design a battery, as I have done, you take the permissible volume and fill it with electrochemically active materials plus electricity carrying circuitry such that provides a maximum amount of electrical energy (Watt hours) to a electrical energy consuming load. And the things that I mentioned are the components of the battery and the electrochemical cells that have to be designed. And as a black box, a battery is considered to an EMF source with a certain amount of watt hour delivery capability and with a certain amount of internal resistance that shares the EMF delivery capability with the external electrical load. And it does that by supplying an EMF voltage at the negative terminal such as to be able to cause a flow of electrons out of the negative terminal into the load resistance.WFPM (talk) 04:24, 18 February 2012 (UTC)

The majority, if not all, of that has no relevance to the discussion of direction of conventional current flow and completely fails to answer Alfred Centauri's points. SpinningSpark 07:30, 18 February 2012 (UTC)

I appreciate your point! But I'm trying to get by the misconception that there is a flow of positive charged flow entities in an electric circuit. In an electrochemical battery, there is a flow of positive ions within the electrolyte, which depletes the energy of the battery. But the function of the battery is to move electrons. And I don't see how you can conceive of positive ion migration as being current flow.WFPM (talk) 20:17, 18 February 2012 (UTC)WFPM (talk) 15:02, 18 February 2012 (UTC) Note that if the battery is rechargeable, you can restore it with energy by using an electrical battery charger to push the electrons back into the cells of the battery and thus restore some of their electricity producing electrochemical activity.WFPM (talk) 21:10, 18 February 2012 (UTC)

Low Potential to High Potential?

I really don't understand the statement "...electric charge flows by means of electrons, from lower to higher electrical potential". In my admittedly limited and basic education on the subject, I thought I understood it like this. Electrons, being all negatively charged have a tendency to repel each other and seek out areas where there are fewer electrons. However, one might think of the empty "holes" that electrons move into as "particles" themselves that have a positive charge. It was established by convention back in the early days then that electrical current is the flow of these positive "particles" in the opposite direction that the electrons were flowing. I've always assumed that an additional part of this convention then is that the high potential end of a circuit means high positive charge and the low potential side of the circuit means low positive (high negative charge). So it's still flowing from high potential to low potential, it's just a matter of convention which is defined as high potential. It doesn't make sense to me that everything else if physics tends to go from high potential to low potential except electric current. I mean when I was a kid I learned about electricity using a water analogy with two tanks with different levels of water attached by a pipe. I can only imagine my confusion if my teacher told me the water would flow from the shallow tank to the more full tank. Like I said, my understanding of the subject is obviously limited and basic. Just think this sentence could be expanded on more. — Preceding unsigned comment added by 69.174.58.28 (talk) 18:28, 19 March 2012 (UTC)

You seem to have answered your own question - negative charge (electrons) move to the higher electric potential. Note that high (positive) potential is a lower energy state for a negative charge. The concept of holes is not a particularly useful one in normal metallic conductors. SpinningSpark 21:39, 19 March 2012 (UTC)

Hmmm, let me try again. You say "negative charge (electrons) move to the higher electric potential". Ok, but that is not what electric current is. Electric current is the positive charge moving to negative not the other way around. So it seems to me that as the convention is defined, current is a positive charge moving from high positive potential to low positive potential. Why go through all the mental gymnastics to treat these holes as positively charged particles that move in the opposite direction than the electrons and define that as electric current, then turn around and say wait, not only is the current flowing from negative to positive it's flowing from low potential to high potential. On the other hand, after reading this a bunch of times now I'm wondering if maybe I'm confusing the terms "electrical charge" and "electrical current". Is it maybe that electrical charge is electrons. And electrons DO flow from low potential to high potential with respect to electrical current which is defined by convention to be the flow of the positive side to the negative? If so, it seems like this terminology was invented by some sort of sadist! ;) I wonder if that could be better explained in the article. — Preceding unsigned comment added by 68.42.68.67 (talk) 04:44, 20 March 2012 (UTC)

The conventional direction of positive current flow was established long before anything was known about the charge carriers themselves. If electrons had been known about at the time, conventional current would probably have been defined in the opposite direction, but it is quite unlikely ever to be changed now - there are thousands of books, hundreds of thousands of engineers and millions of measuring instruments all using the current system. Which direction is chosen does not actually make any difference to any aspect of circuit analysis, and it at least has the advantage of forcing students to realise that charge carriers can be both positive and negative and to consider the implications. The bottom line is that the Wikipedia article should reflect the practice of the field, it is not our place to try and invent something better.

I'm not sure what you mean by "Is it maybe that electrical charge is electrons. And electrons DO flow from low potential to high potential with respect to electrical current which is defined by convention to be the flow of the positive side to the negative?" The opening statement of the article is "electric current is a flow of electric charge through a medium.[1] This charge is typically carried by moving electrons in a conductor such as wire" together with the opening paragraph of Conduction mechanisms section seems to entirely explain your difficulty. Can you suggest an improvement? SpinningSpark 10:11, 20 March 2012 (UTC)

Thanks, I appreciate your replies and patience. I definitely was not suggesting that the conventions should be changed. My point was just that, layman though I am, I consider myself a fairly intelligent person and I'm still confused after reading over the article and your comments many times. So unless wikipedia is only meant for those steeped in the subject matter already, I just wondered if there was some way to clarify it in the article. As for suggesting an improvement, I suppose I could try. However, as confused as I am I don't have much confidence that it would even be correct. With that caveat, here is my attempt:

By convention, the direction of electrical current flow is defined as a positive charge flowing towards a negative charge. However, when discussing high potential vs low potential in electrical circuits, high potential always refers to the higher negative charge. This is because the negative charge is a higher energy state than a positive charge, a positive charge simply being the absence of electrons (negative charge). This might perhaps create some confusion for the lay person because it implies that conventional current flows from low potential (positive charge) towards high potential (negative charge). This is possibly counter-intuitive to those who are accustomed to other physical phenomena where objects have a tendency to move from higher potential energy states to lower potential energy states. However, it should be noted that this apparent contradiction is simply due to the definition of current flow as positive to negative which is really an arbitrary definition adopted long before anybody even knew about electrons.

Or something like that... And if that's not right I give up :)... One last thing, though. If it IS right, I still think the statement "...electric charge flows by means of electrons, from lower to higher electrical potential" is still problematic. If I go to the wiki page for "electric charge" it says in the 2nd sentence "Electric charge comes in two types, called positive and negative." So it seems like it would be more accurate to say "...POSITIVE electric charge flows from lower to higher electrical potential". Unless I'm still hopelessly confused (which is a possibility), negative charge does not flow from low potential to high potential. — Preceding unsigned comment added by 68.42.68.67 (talk) 05:00, 21 March 2012 (UTC)

Almost every statement you have made there is wrong, but it would take too long to address them all point by point. The heart of the matter seems to be that you do not understand what electric potential is. In an electric field, work must be done to move a charge against the field. Electric potential of a point is defined as the work done (per unit charge) in moving a small test charge to that point. It is measured in volts. A positive charge moving towards a lower potential (could be negative or just less positive) is moving in the same direction as the direction of the field, not against it, and is thus losing potential energy, but gaining kinetic energy, just like a ball falling in a gravity field. A negative charge moving towards a higher potential is also losing PE and gaining KE. Although the movement is against the (conventional) direction of the field, the charge is negative and Force = charge x field strength. Thus the force is also negative - meaning it is acting in the same direction as the charge motion, causing a gain in KE. A double negative is a positive. SpinningSpark 12:34, 21 March 2012 (UTC)

Ok, I know this forum isn't meant for you to educate me on the subject so I'll just take one last stab and leave it at that. Regarding electrical potential I thought I understood it before this conversation. And your explanation in your last comment actually makes a lot of sense to me. When you say in both cases they are losing PE and gaining KE, that actually jibes with the way I've always thought about it. But to me, almost by definition something that is losing PE and gaining KE is moving from high potential to low potential. It doesn't really bother me that they'd both be going from high to low because it's all a matter of perspective. From the perspective of a negative charge, high potential is the more negative side and low potential is the more positive side and vice versa. I've always thought of it as the charges are kind of swapping places trying to reach equilibrium on both sides. So you can define high potential/low potential either way. Now, I notice in your explanation, though, that you referred to the high potential as the more positive side in both cases. That doesn't make sense to me unless you are simply saying, look, you've got to pick one or the other and by convention with respect to direction of current flow, high potential is always defined as the high positive charge. If that's what's going on then I'm totally fine with that. That's what I thought it was back in my very first comment. But here's my problem with the statement "...electric charge flows by means of electrons, from lower to higher electrical potential". It's too broad. If I've finally got this right, not all electric charge goes from low potential to high potential. Only negative electric charge goes from low potential to high potential. A positive charge will flow from high potential to low potential, am I right? If the sentence said "...negative electric charge flows by means of electrons..." or "...electrons flow...", then I would have had to think about it a bit but I think I'd have figured it out. As it stands, I read it and thought to myself, huh? That's different from every explanation I've heard about electricity since I was in the 4th grade. Everybody knows current flows from high potential to low potential. That's what voltage is, the difference in electrical potential. If it flowed from from low to high my 9 volt battery would be labeled a -9 volt battery, etc., etc. etc. Anyway, that's my more than 2 cents worth. — Preceding unsigned comment added by 68.42.68.67 (talk) 00:43, 22 March 2012 (UTC)

Edit request on 8 December 2012

Conduction in semiconductor devices may occur by a combination of drift and diffusion, which is proportional to diffusion constant and charge density . The current density is then:

The formula one line below has error. The term \Alpha_q is missing ; should be D \Alpha_q q \Grad n

212.117.154.242 (talk) 08:50, 8 December 2012 (UTC)

The formula is correct - diffusion current is proportional to the charge density gradient, not just charge density. The sentence above that equation is misleading though. Comments? Materialscientist (talk) 10:50, 8 December 2012 (UTC)

Opening paragraph

I haven't checked this article in quite a while. The opening sentences are now:

An electric current is a flow of electric charge through an electrical conductor.[1] Electric charge flows when there is voltage present across a conductor.

A question and an observation:

(1) is it then the case that the electric charge flowing through a vacuum, e.g., between the cathode and plate of a vacuum tube, is not an electric current?

(2) electric charge can flow through a superconductor when there is no voltage present and, in fact, there can be no voltage present across an ideal conductor for any amount of electric charge flow.

Alfred Centauri (talk) 23:14, 22 March 2013 (UTC)

Electric charge flowing through a vacuum is really not a vacuum and it is a plasma.Embrittled (talk) 01:40, 23 March 2013 (UTC)

That's not actually the case. When the vacuum tube is in "cut-off", the electrons are confined to the vicinity of the cathode. Only when the tube is conducting are the electrons flowing through the vacuum to the plate. Moreover, a plasma is an essentially charge neutral conducting medium.

From Britannica: [A plasma is an] Electrically conducting medium in which there are roughly equal numbers of positively and negatively charged particles.

From Columbia Electronic Encyclopedia: [A plasma is a] fully ionized gas of low density, containing approximately equal numbers of positive and negative ions.

Also from Vacuum Tube: [A vacuum tube] is a device controlling electric current through a vacuum in a sealed container.

In a vacuum tube, the electrons form a current through a vacuum, not through a plasma. Alfred Centauri (talk) 15:04, 23 March 2013 (UTC)

In order to create a flow through a superconductor you need to have an EMF to start with, but you can keep it going after the EMF is removed for quite a while (but not indefinitely.) You can also create currents that persist for a short while in normal conductors (eddy currents), which are kept going by inductance, the inductance creates a small EMF. Superconductors are really more similar than you would think.Embrittled (talk) 01:40, 23 March 2013 (UTC)

Even superconductors have a very, very, very low resistance, not perfectly zero.Embrittled (talk) 01:40, 23 March 2013 (UTC)

Electric current is the flow of electric charge. It is still electric current whether the charge is flowing in a conductor, superconductor, insulator, insulator in breakdown, or vacuum. There is no need for any qualifying clauses to the statement. I have removed this from the article along with the source which really cannot be considered definitive for our purposes (Projects by Students for Students). There are plenty of textbook alternatives if these are really needed.[1][2] The argument that a vacuum is no longer a vacuum if it has charges in it is specious. This may be meaningful in philosophy (and possibly relativity) but here it is merely playing with semanitics. SpinningSpark 17:50, 23 March 2013 (UTC)

Canada?

The article says the original definition of current does not stand in Canada? Are physics different up there? Maybe it's like toilets spinning backward in Australia? Kaz 00:17, 8 Feb 2005 (UTC)

Can someone back this up? I cite this as evidence that conventional current is used: http://www.control.toronto.edu/courses/110/solu.summ.2001/quiz3.may29.pdf

I removed "(Notably, this is not the case in Canada)." until someone can verify it. - Omegatron 03:44, Mar 4, 2005 (UTC)

Someone is confused. In Canada, the standard definition is used. What do you mean by "the physics is different up there?" The concept of current flow from + to - is just a convention. If you are talking about what is actually flowing in a circuit, then that is about actual physics. Vmelkon (talk) 06:00, 26 June 2011 (UTC)

Someone is making a tongue in cheek comment and someone else is not "getting it". — Preceding unsigned comment added by Longinus876 (talk • contribs) 16:54, 6 October 2013 (UTC)

Current Flow

The term Current is defined as the flow of electric charge. As such the using the expression "Current Flow" would mean the flow of the flow of electric charge. Unless we are using the expression to explain charge acceleration, the expression is being used in a grammatically incorrect fashion. In this article under the section resistive heating I have attempted to fix this grammar mistake twice. Each time being reverted. This section describes an experiment where a known current is passed through water. While the current is varied for datapoints, it is fixed for a time period so the rate of temperature change can be measured. In this case the Current is assumed to be constant and not flowing for a particular temperature change. Ergo the use of the term "Current flowing" is grammatically incorrect. --Kyohyi (talk) 22:22, 25 September 2013 (UTC)

"Current flow" is an extremely common and broadly well understood term. Your removal of this, in favour of a convoluted construction calculated to confuse our readers is about as helpful as it would be to reverse the direction of conventional current because it was more correct. "conventional current is defined to be in the same direction as positive charges" is particularly ugly. This is not grammer_(sic), it is semantics. Andy Dingley (talk) 13:58, 26 September 2013 (UTC)

Actually "Current flow" is an extremely common and broadly misunderstood term. The term Current is already a description of the flow of charge. This article already explains this. As such Current has a magnitude and an implied direction. A flow of current would mean the flow of the flow of charge, this concept is discussed in this article under the section drift speed. My removal of the term flow was not designed to confuse but to be consistent with the definition of current. --Kyohyi (talk) 14:25, 26 September 2013 (UTC)

I'm both an engineer and a linguist, and all I can say is that Andy is right and you are wrong. Language does not work like mathematics: the "correct" form is ultimately determined by usage, which is overwhelmingly on the side of "current flows". Current flows even in IEEE papers [3], so changing it to is can only be perceived as 'bizarre', to quote Andy. Wikipedia does not WP:RIGHTGREATWRONGS. No such user (talk) 18:44, 26 September 2013 (UTC)

Then I recommend you read the article you linked to. The paper uses both the terms current and current flow. It's not righting great wrongs to have the wikipedia article concerning current be internally consistent with it's own listed definition. --Kyohyi (talk) 19:27, 26 September 2013 (UTC)

I don't know that the phrase 'current flow' is wrong, it's like saying the 'run of the runner'. But it clearly is redundant, since the current is a flow.GliderMaven (talk) 19:55, 26 September 2013 (UTC)

If I may ask folks, what is your background? Because for anyone with engineering or physics education, current is the thing that flows. The word current maybe originates as a synonym for flow, but when it describes a physical quantity, it acquired a meaning of its own, just like voltage or river. And my IEEE sample was just one of many: [4] -- true, in many of those word flow is used as a noun, but that still goes against your argumentation, that it would be the same as flow flow. Well, it isn't. Besides, sentence like "current is defined to be in the same direction as positive charges." is just awkward and does not... flow. No such user (talk) 22:42, 26 September 2013 (UTC)

No, for anyone, such as myself with a physics or engineering background, a current is a vector velocity field, and is not the thing that flows, it is the flow. The phrase 'current flow' is therefore redundant. Googling the term I find that the better the source is, the less likely they are to use the term 'current flow', presumably for this very reason.GliderMaven (talk) 03:50, 27 September 2013 (UTC)

Human language sometimes involves redundancy (linguistics), quote: "redundancy increases the odds of predictability of a message's meaning and understanding to others. Redundancy typically takes the form of tautology: phrases that repeat a meaning with different though semantically similar words. Common examples are: "a variety of different items", "an added bonus", "to over-exaggerate", "and etc.", "end result", "free gift", "future plans", "unconfirmed rumor",[...]". I don't know where your assertion that "the better the source is, the less likely they are to use the term 'current flow'" comes from, but thousands of authors at Google books don't seem to have a problem with it: https://www.google.com/search?q=%22current+flows%22&btnG=Search+Books&tbm=bks (I stopped checking at page 100). It can't be that thousands of authors and their lectors made a slip. Avoiding the term is completely unnecessary pedantry, and just results in stilted and artificially sounding sentences, like the one above. No such user (talk) 12:24, 27 September 2013 (UTC)

In the cases you quote of redundancy the intention is to repeat the meaning for emphasis. We have no need for emphasis here; so 'current flow' is more like 'PIN number'.GliderMaven (talk) 12:53, 27 September 2013 (UTC)

No it's not, you're reading it selectively. It just "increases the odds of predictability of a message's meaning and understanding to others". When you have word current as subject of a sentence, you need a verb with it, and is is not the one which is adequate for all purpose; so people go with flow. Stating that current flows from positive to negative is just a Plain English way to express a simple concept. No such user (talk) 17:31, 27 September 2013 (UTC)

When current is generally being used in the expression of "current flow" current is taken to mean electric charge, or charge. When we use the expression "current flow" in this article we create a second implicit definition of the word current. Seeing as this article is about the explicit definition fo Current, the use of the implicit definition of current makes the concept ambiguous, and the implicit version should be removed for clarity. --Kyohyi (talk) 18:08, 27 September 2013 (UTC)

And it's even worse than PIN number which is wrong, because 'current flow', unlike the examples you quote, means something else, the flow of a flow is the vector field that is the CHANGE in the flow over time, which is certainly an interesting and useful concept, but isn't what the article is about. Some fraction of the readers will actually get that, and may get confused, unless you define your terms (and I don't think you'll find a reference for that definition). It's doubtless a bad idea to knowingly use incorrect terminology like that.GliderMaven (talk) 12:53, 27 September 2013 (UTC)

You still haven't addressed the substance of my argument, which is that millions of English speakers, including many quite educated in the matter, do not seem to subscribe to the alternative interpretation you propose, and are not confused with the phrase, which is evidenced by the number of Google hits on web, Scholar and Books. Our rather comprehensive article List of English words with disputed usage does not mention the issue. How come they are all suddenly wrong and you're right? I don't buy the "it's not logical" arguments in the matters of language, because the language is not always logical. Do you have an authoritative source which discusses the inadequacy of the term? So far, I have seen only WP:IDONTLIKEIT. No such user (talk) 17:31, 27 September 2013 (UTC)

Those alleged 'millions' notwithstanding, a minority of sources I checked use this phraseology, and it is clearly inaccurate and potentially confusing. I was unable to locate an authoritative source that defines the meaning of the phrase 'electric current flow', but I was able to find definitions of 'electric current' and 'electric charge flow' which we can use instead and do not share these drawbacks. Given that, I do not support the usage of this phrase in this article.GliderMaven (talk) 00:44, 28 September 2013 (UTC)

The sentence now reads: "The direction of conventional current is defined arbitrarily to be the direction of the flow of positive charges." I would put the words 'same' and 'purely' or 'only' in there somewhere, but that sentence otherwise seems pretty reasonable to me.GliderMaven (talk) 12:53, 27 September 2013 (UTC)

That much I could agree. No such user (talk) 17:31, 27 September 2013 (UTC)

Perfect examples of why students run away from this subject. "Current flows, current is the flow"; Embarassing. How many angels fit on the head of a pin? — Preceding unsigned comment added by Longinus876 (talk • contribs) 17:15, 6 October 2013 (UTC)

The construct current flow where flow is noun could just as well be changed to current without confusing anyone. I would not oppose that, however I only saw one occurrence in the article. On the other hand "current flows" where flows is a verb is very common. If we substitute charge flow for current we get charge flow flows. So here, flow is a noun and flows is a verb and what we are saying is that the flow does what it does which is that it flows. But let's use it in context. Suppose we have "The current flows mainly in the ground strap" Making the substitution we get "The charge flow flows mainly in the ground strap" There is no inherent logical conundrum. We could of course say "The current is mainly in the ground strap" and in a scholarly article you might say that. After all, we have no problem saying "the voltage is ... ". But, we say current flows because in our mind current is a collection of things actively doing something (flowing) and voltage is more like a parameter, like height. Although height can change, we don't think of height as doing something. So, height is and voltage is but current flows.Constant314 (talk) 02:24, 16 October 2013 (UTC)

The problem with Charge flow flows is that it means that the charge flow is changing, there are some instances where this is happening, and there are instances where it is not. To emphasize my point, what would be the current flow of a circuit that has a 5V constant voltage source through a 1 ohm resistor? Assume steady state conditions. --Kyohyi (talk) 13:23, 16 October 2013 (UTC)

"The problem with Charge flow flows is that it means that the charge flow is changing" – no, it does not mean that. It takes a quite convoluted reading to achieve such conclusion. No such user (talk) 14:25, 16 October 2013 (UTC)

If it doesn't mean that, then what does it mean. Instead of just shutting down discussion with a statement offer your own explanation. --Kyohyi (talk) 16:34, 16 October 2013 (UTC)

Is English your native language? I ask because you appear to have difficulty in accurately parsing a sentence, yet you then proceed to impose your misinterpretation onto others, rather than realising you might be mistaken. These words: they do not mean what you think they mean. Andy Dingley (talk) 17:20, 16 October 2013 (UTC)

If you can't offer anything constructive please stay out of the discussion. And if you have an assertion as to their meaning please put it forward, otherwise you have no argument, and your participation is nothing but disruptive. --Kyohyi (talk) 17:27, 16 October 2013 (UTC)

Your main error is that you seem to think that the same logic from mathematics can be applied to language. For example, in mathematics, $a=b\land b>c\implies a>c$. Applying that logic to the language, (current)=(charge flow) and (current)⊕(flows) implies (charge flow)⊕(flows). However, that does not work in a general case. Unlike "current flows", the expression "charge flow flows" is gibberish. The idiom (or, rather, collocation current flows apparently originated -- or is, at least, formed by analogy -- as a metaphor of water flows (see hydraulic analogy). From e.g. Britannica [5]: "Gulf Stream, warm ocean current flowing in the North Atlantic ". By your logic, that would be inapplicable, because "current" = "water flow", therefore "current flowing" = *"water flow flowing". Guess what? That does not work. If it worked, we wouldn't have idioms in language.
Yes, Wikipedia articles should generally strive for accuracy and precise language. But they are also aimed for the general public, an the text should be understandable to the layman; precision must not come on expense of clarity and naturality of expression, particularly when it creates no plausible ambiguity. No such user (talk) 06:58, 17 October 2013 (UTC)

Current flow when used in electrical engineering is Jargon, the meaning of the expression is not consistent with the definitions of the words, and without existing knowledge of the concepts the expression makes no sense. What's more, the literal definition of the expression, the one you think is gibberish, actually describes a concept that is important in electrical engineering. A transformer is just another strip of wire if we didn't have a current that changes. If how the currents were changing were an important concept in ocean flows then we could make that comparison, however a changing current, and how that current changes is an extremely important concept in electrical engineering. --Kyohyi (talk) 13:39, 17 October 2013 (UTC)

From WP:JARGON: Some topics are intrinsically technical, but editors should try to make them understandable to as many readers as possible — that does not match your definition of "jargon". As evidenced by the number and profile of Google hits, "current flows" is not a technical jargon, but an everyday, common English term understood and used by laypersons and scientists alike. On the contrary, it is only you who tries to apply a meaning from technical jargon to it — nobody in the world would interpret "current flows" as "amount of charge changes". When we mean that magnitude or direction of current changes, we say that it changes, not that it flows. No such user (talk) 15:27, 17 October 2013 (UTC)

Use does not equate understanding. Demonstrating that laypersons use the expression doesn't mean that they have any idea as to what they are talking about. They are merely mimicking the jargon being used by those in the field. Current flow, where flow is a verb connotes action onto current. In the circuit example I showed above, what is the action that current is taking? The misunderstanding behind this expression is that current is used in place of charge. Then we have discussions about changing current where it is really changing charge that is the subject. The Jargon comes from that you have to already know this switch to actually understand the conversation. The confusion really becomes exemplified when we really do deal with subjects that are about changing current. --Kyohyi (talk) 16:34, 17 October 2013 (UTC)

At this point, I must conclude that your attitude is that you are right and the whole world is wrong. Known in Wikipedia jargon as WP:IDIDNTHEARTHAT. No amount of rational argument can be spent changing that. So I guess I will stop wasting my time. I suggest you join your fellow know-better-than-everyone fellow linked in #A small digression, below. No such user (talk) 17:42, 17 October 2013 (UTC)

flows doesn't mean changing. If it did then charge flows would be nonsense.Constant314 (talk) 03:56, 17 October 2013 (UTC)

Change in position, movement. The location of the charge has changed. A change in the amount of charge. These are all descriptions of charge flow. --Kyohyi (talk) 13:41, 17 October 2013 (UTC)

Then let's add a time element. Before the battery was connected, the current was zero. Then when it was connected a new value for the current flowed through the wire and the components.Constant314 (talk) 01:50, 18 October 2013 (UTC)

If there is a time element then yes, but are we talking about time varying current? Especially in sections about DC are we not dealing with steady state conditions? --Kyohyi (talk) 13:19, 18 October 2013 (UTC)

The plan is to change the uses of 'current flow' to 'charge flow' not to change 'current' to 'charge flow'. Note that current flows or charge flow flows (if you must) actually do happen if you move a magnetic field across a conductive sheet.GliderMaven (talk) 14:48, 16 October 2013 (UTC)

Perhaps we should discuss a specific case. I suggest you pick out what you consider to be the worst usage of current flow in the article and lets discuss that instance.Constant314 (talk) 04:15, 17 October 2013 (UTC)

Most cases are a relatively simple swapping of terms, however this sentence in the direct current section "Direct current may flow in a conductor such as a wire, but can also flow through semiconductors, insulators, or even through a vacuum as in electron or ion beams." would be the worst case. My understanding of what they are saying is that we can have Direct Current through wires, semiconductors, insulators, and through a vacuum as electron or ion beams. --Kyohyi (talk) 19:29, 17 October 2013 (UTC)

Do you, or do you not, understand the linguistic difference between "current flow" and "current may flow"? – and I don't just mean the conditional. Andy Dingley (talk) 23:14, 17 October 2013 (UTC)

I suggest we instead spend time improving Wikipedia rather than arguing the toss about trivial differences in wording.GliderMaven (talk) 13:21, 17 October 2013 (UTC)

I found these uses of current flow in some books I had lying around:

Electronics Circuits: Discreet and Integrated (college text book) by Schilling and Belove, 1969 uses "current flow" on pages 10, 20,73 and 75. Uses "currents ... flowing" on page 75. Uses "current will flow" on page 13.

Operational Amplifiers, by Tobey, Graeme and Huelsman, 1971 uses "flow of current" on page 36.

Analog Design by Jim Williams, "Ic4 will flow" on page 134.

Art of Electronics, 2nd Ed by Horowitz and Hill, page 2 "current in a circuit is considered to flow..."

Principals of Radar by M.I.T. Radar School Staff, 1946, page 2-16 "grid current flows".

RF Circuit Design by Ludwig and Bretchokm, 2000, uses "current flow" on pages 49 and 50.

High Speed Digital Design by Johnson & Graham, 1993, page 12, "leakage current flows"

I'd say that two thirds of all the books that involve electronics that I looked have a form of "current flow: or "current flows" in it.Constant314 (talk) 08:06, 27 October 2013 (UTC)

This is a really silly debate. Kyohyi, GliderMaven, there is no ambiguity about what the term means, it is just an idiom, like "running for office". You are not going to change an idiom that has been in use for 150 years, and there is no reason to. Even if you could, this is not the place to do it. This is a technical article, not a linguistic article. WP is an encyclopedia; we have to follow established usage, we can't make up our own. If you have a problem with the term, take it up with the Institute of Electrical and Electronic Engineers. --Chetvorno^TALK 20:28, 4 November 2013 (UTC)

Yes, it's an idiom, and in general, idiomatic language is within reason, best avoided. If the, rather clearer and more accurate replacements were unduly cumbersome, you would have a point, but they are not.GliderMaven (talk) 20:48, 4 November 2013 (UTC)

No such user above pointed out that the redundancy in idiomatic phrases such as "end result", "free gift", "unconfirmed rumor", "to over-exaggerate", and "current flow" reinforces and clarifies their meaning, it doesn't obscure it, which is why these idioms came to be used in the first place. --Chetvorno^TALK 22:11, 4 November 2013 (UTC)

A small digression

I apologize for violating WP:NOTAFORUM, but I couldn't resist... In search for a debate about (in)appropriateness of the term "current flows", I googled "current does not flow" [6], and the third hit was [7]:

“ Even more often, the word "current" is incorrectly used instead of "electricity", as in "flow of current" (but a current is a flow. Are rivers full of current? No, water. Flow of "charge" is correct, flow of "current" is not. ”

The whole article is actually a rant about "incorrect" use of electricity-related terminology, prefaced with "Below are my original, very crude and unedited 1989 notes... [...]Why are my explanations different than usual? Because they're based on the defeating of misconceptions: on the painful 'unlearning' I had to go through before I could understand simple electrical physics.", and hosted on website "Science Hobbyist". No other relevant hits in the first couple of pages, which don't have a problem with "current flows"...No such user (talk) 07:29, 17 October 2013 (UTC)

Charge transport, spin transport

"Electrical currents transport charge, but certain experimental setups allow them to transport spin as well."

AntiqueReader (talk) 03:34, 5 February 2014 (UTC)

We have an article at spintronics. SpinningSpark 19:06, 5 February 2014 (UTC)

amperage?

"amperage" redirects to this article, but amperage is never mentioned in the article.

The dictionary says that amperage is the strength of an electric current, but that's hardly a complete explanation. 69.150.11.22 (talk) 21:47, 7 March 2014 (UTC)

It's simply a rather informal expression for an amount of electric current measured in amperes. Similarly, wattage redirects to electric power. There is really not any more to say about it than the dictionary definition and Wikipedia is not a dictionary, we have Wiktionary for that. SpinningSpark 23:59, 7 March 2014 (UTC)

but direction when the opposite some time they are i mean charge is equal run i saw this — Preceding unsigned comment added by 182.188.193.87 (talk) 17:36, 15 March 2014 (UTC)

Metals: free electrons, conduction electrons

The sentence "A solid conductive metal contains mobile, or free electrons, originating in the conduction electrons" is a bit awkward. Assuming the Wikipedia articles about free electrons and conduction electrons is correct it would seem that any material can have conduction electrons given enough energy but free electrons are only found in metal where they also function as conduction electrons. Or maybe they are conduction electrons. I'll change it to function as. Someone who knows better is welcome to fix it better.Constant314 (talk) 23:16, 20 March 2014 (UTC)

Electromagnet: special relativity.

The sentence "The theory of Special Relativity allows one to transform the magnetic field into a static electric field for an observer moving at the same speed as the charge in the diagram." is incorrect or ambiguous for the diagram. Probably one would need a speed where the current of electrons going one way was equal to the current of atomic nuclei going the other way. Anyway, SR transformation of the magnetic field is probably out of scope for an article on current.Constant314 (talk) 23:32, 20 March 2014 (UTC)

I think it is reasonable to have a mention of SR here, or at least a link to an explanatory article for readers who wish to know more. It is no more out of scope than the following section on radio waves. The magnetic field is intrinsically linked to current flow, it is inseparable from it, and SR is required to fully understand this. By the way, you are mistaken in thinking that a frame where the positive and negative charges have equal and opposite velocities would result in the magnetic field transforming to zero. The currents of the two lines of charges have equal and opposite velocities, but because the charges are of opposite sign both currents are equal (ignoring relativistic foreshortening which will be negligible at the velocites involved in regular conductors) and in the same direction. Thus their magnetic fields will add. I do not believe that the magnetic field of an overall neutral current carrying conductor can be transformed to zero in any frame. Nor can the current be transformed to zero if it was not zero in the rest frame. SpinningSpark 16:06, 26 March 2014 (UTC)

Yes, the currents would add and the field would not cancel. I'll stick with the sentence being "incorrect or ambiguous". As for scope, I think SR is two steps away. An article on current could reasonably discuss magnetic fields and an article on magnetic fields could reasonably talk about SR. But I would not object to a statement or section that was factually correct and not misleading on the grounds of scope.Constant314 (talk) 22:29, 26 March 2014 (UTC)

International System of Quantities

The International System of Quantities (ISQ) is not the same as the International System of Units (SI). Furthermore, the ISQ is defined by the BIPM as "system of quantities having the base quantities: length, mass, time, electric current, thermodynamic temperature, amount of substance, and luminous intensity", making it directly relevant to this article. Dondervogel 2 (talk) 16:53, 7 April 2014 (UTC)

I've reverted, I guess you're right. SpinningSpark 22:26, 7 April 2014 (UTC)

Suggestions, since article is semi-protected

• "In metallic solids, electric charge flows by means of electrons, from lower to higher electrical potential."

In a simple battery-resistor circuit, electrons flow from negatively charged battery terminal to positively charged battery terminal. This is the (spontaneous) direction of flow, in which battery discharges. Positively charged terminal is the high potential terminal for conventional flow and low potential terminal for electron flow. Whatever you assume to be flowing (positive or negative charge carriers), the flowing thing is moving from a point of high electric potential, towards a point of low electric potential. This is the natural direction of flow; from high potential to low potential: For a falling rock, gravitational potential energy decreases; for (spontaneous) thermodynamical processes, thermodynamic potential of the system decreases; for orbiting bodies (macro or micro), force field moves the body in the direction of decreasing potential energy associated with the field (gravitational or electrostatic). Potential energy (of any kind) is the energy stored in the force field; when the state of the object is allowed to be altered only by the field, the potential energy decreases. This is the meaning of "potential energy"; it decreases in spontaneous processes/flows, among which is the discharging of a battery.

If you are an electrical engineer and (probably because of that) considering conventional flow, charge carriers have positive charge, and they flow from high potential terminal (positively charged terminal) to low potential terminal (negatively charged terminal).

If you are solid state physicist and (because of that) considering electron flow, charge carriers have negative charges, and they flow from high potential terminal (negatively charged terminal) to low potential terminal (positively charged terminal).

By convention high electric potential always means more positive and low potential means more negative, so positive charge carriers tend to flow from high potential to low potential and negative charge carriers tend to flow the other way. That is the convention whether you are an engineer or a physicist.Constant314 (talk) 23:03, 20 March 2014 (UTC)

Finally, "electric charge flows by means of electrons": How about, "flowing electric charge is carried by electrons", or "electrons are the flowing charge carriers", or "electric charge is carried by electrons".

I don't see a great difference in all these possibilities so I'm inclined to leave it the way it is.Constant314 (talk) 23:03, 20 March 2014 (UTC)

• "In electronics, other forms of electric current include the flow of electrons through resistors or through the vacuum in a vacuum tube"

Is there something that separates electric current through a 1.5mm copper wire and electric current through a 10 megohm ceramic resistor. The resistance mechanism is lattice scattering in DC, whereas skin and proximity effects (self&externally induced eddies) join the club in AC, and club changes the name to impedance. This is the way a conducting medium resists to flowing charge carriers: Lattice atoms in thermal motion scatters flowing charge carriers, and an alternating magnetic field (if-exists) induces eddy currents. So, how about we stop considering "flow of electrons through resistors" as 'another form of electric current'. Or, while we are at it, we could also list a few other circuit elements to enrich the content, e.g., electric current through inductors, electric current through diodes, electric current through human body, etc.

Off hand, I would not expect the conduction mechanism of resisters to be a lot different from metals, but the rest of the sentence does not seem too redundant. And there is the "excess noise" effect in some resisters so there may be indeed some other type of conduction, but there does not seem to be any point of mentioning without explaining it. It probably could use some wordsmithing, but its not egregiously incorrect.Constant314 (talk) 23:03, 20 March 2014 (UTC)

• "The theory of Special Relativity allows one to transform the magnetic field into a static electric field for an observer moving at the same speed as the charge in the diagram. The amount of current is particular to a reference frame."

How about, "the same speed as a flowing charge" instead of "the same speed as the charge in the diagram".

That whole sentence needs work. It looks like it was tacked on after the figure was added. I'm inclined to delete it.Constant314 (talk) 23:03, 20 March 2014 (UTC)

• "A solid conductive metal contains mobile, or free electrons, originating in the conduction electrons."

If you call it metal, you implicitly call it conductive (or conductor), and vice versa depending on the context.

Acceptable redundancy. Not obviously implicit to everyone.Constant314 (talk) 23:03, 20 March 2014 (UTC)

'free electrons originating in conduction electrons': Both the introductory text of Callister, and Kasap's graduate text avoids using "conduction band", in text and in diagrams, for metals; metals do not have an energy gap between occupied energy states and free energy states, semi-conductors and insulators have the gap. Valence electron is not a free electron, a free electron is an electron excited to one of the emtpy energy states by an applied electric field. When a valence electron is freed, it becomes a free-electron.

At least, how can it "originate in conduction electron", i do not know. ('originate in' or 'originate from'?) — Preceding unsigned comment added by 85.110.37.26 (talk) 12:28, 20 March 2014 (UTC)

Yes, it does not make sense as written.Constant314 (talk) 23:03, 20 March 2014 (UTC)

In the section about reference direction, what exactly is meant by the term "positive current"? I guess it means the direction of the flow of positive charges but it could mean the direction of the flow of charged particles - it wouldn't go amiss to be clear about this.Quill14 (talk) 23:06, 12 November 2014 (UTC)

It is the direction positive charges are going or opposite the direction that negative charges are going. If a wire has 1 amp of electrons moving from right to left, I can draw the current vector right to left or left to right. If I draw it in the same direction that the electrons are moving, then the numerical value of the current vector is -1 Amp. It is negative because the charge carriers are negative. If I draw the vector the the other way, I have to also reverse the sign of the numerical value to +1 amp. Which is a long way of saying that the direction of positive current is the direction in which the numerical value for the current vector is positive.Constant314 (talk) 00:05, 13 November 2014 (UTC)

Light radiation

"Electric currents can result in the radiation of heat and light." - [8].

While it is technically true, this is misleading. Current can cause light by two effects :

• light emitted by incandescence is due to heat, which is itself due to the current by Joule heating ; contracting the causality link is disputable, even for a lead section.
• alternating current emits radio waves (ie electromagnetic radiation), and "light" is a particular kind of those waves : the ones with wavelength in the 400-700 nm range (roughly). A back-of-the-enveloppe calculation shows that those wavelengths correspond to frequencies of the order of 10^15 Hz, way out of the usual range for electric currents (home electricity is ~50Hz, basic oscilloscopes go up to the GHz range (10^9 Hz)). I doubt anyone except maybe optics experimentalists have ever seen light from alternating current...

I changed the lead to something less, hmm, misleading.Tigraan (talk) 12:31, 9 February 2015 (UTC)

Conventional current explanation is incorrect

"The direction of conventional current is arbitrarily defined as the same direction as positive charges flow."

This is widely believed, but it is wrong, and it is a misunderstanding of the definition of current.

The only arbitrary convention is that charge (unit: Coulomb) is defined in such a way that electrons have a negative amount of it.

Current is defined as the rate of flow of charge. Movement of electrons in a particular direction is a flow of negative charge in that direction, and the rate of flow of that charge in that direction must therefore be negative. The direction of positive current must therefore be in the direction opposite to electron flow.

There's no trick, no additional arbitrary current direction convention. It's just simple algebra. Gwideman (talk) 17:28, 17 February 2016 (UTC)

You have that the wrong way round old fruit. Conventional current flow is much older than the discovery of the electron. The electron was assigned a negative charge to be compatible with conventional current flow, not the other way around. SpinningSpark 18:36, 17 February 2016 (UTC)

What did I have the wrong way around? I said nothing about the order in which these phenomena were discovered, and of course charge and current were recognized before electrons. My point was that the charge of electrons and the direction of positive current are compatible, not alternative competing conventions. Once a particular polarity of charge was established (which *was* arbitrary), the current direction and electron polarity is determined in the way which matches. Gwideman (talk) 08:28, 16 July 2016 (UTC)

I think conventional current has two meanings that overlap. Current, in a wire, is effectively charge density (coulombs / meter) times velocity (meters / second). If you draw the arrow in the direction the charges are moving, then value of current is negative (negative charge times positive velocity). If you draw it in the other direction, then its value is positive.

The other convention regards choosing a reference direction arrow in a circuit. When a circuit is being solved, reference directions for the currents are chosen arbitrarily. The solution may produce positive or negative values. It is conventional, as a matter of convenience, to try to choose those reference directions such that the currents have a positive value. And, in fact, after the solution is determined, the reference directions be inverted so that the currents have positive value.

In a battery powered circuit, conventional current flows out of the positive terminal. It is also conventional to choose a reference direction arrow for the current coming out of the battery that points away from the positive terminal. However, some people will choose the reference direction arrow such that it points into the positive terminal. In that case the value of current is negative.Constant314 (talk) 16:35, 16 July 2016 (UTC)

I’ve had the same thought. That the electron has a negative charge is, today, accepted without argument. If you have a current of electrons moving from right to left in quantity of 1 coulomb/sec and draw the arrow from right to left, then you have to label it -1 amp with the minus sign required because the sign of the electrons is negative. If you want to label it +1 amp, then you have to draw the arrow the other way. It might be worthwhile to note that if the direction of conventional current were reversed then the sign of the electron would have to be reversed.Constant314 (talk) 14:27, 18 February 2016 (UTC)

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Semi-protected edit request on 17 June 2016

Please change in the section Current measurement , the device for current measurement as Transformers into Current transformer which is the more specific device that is used to measure the electric current.

• Current Transformers (however DC cannot be measured)

Sathish.polimi (talk) 15:28, 17 June 2016 (UTC)

Disambiguation is done. — Andy W. (talk · ctb) 00:08, 18 June 2016 (UTC)

• The article contains:

"Current measurement ...

... Transformers (however DC cannot be measured)"

DC Current CAN be measured, usually by the force on a coil located in a magnetic field.

Transformers are used in AC circuits, not DC. 70.27.152.243 (talk) 03:36, 20 July 2016 (UTC)

It is just saying that transformers can be used for AC current measurement but not DC current measurement. I supposed it could be improved to "Transformers (for AC current only)". Constant314 (talk) 04:12, 20 July 2016 (UTC)

There are current probes which can measure the DC current through a wire, though the magnetic field around that wire, through a ferrite core and Hall effect device. Gah4 (talk) 10:23, 10 January 2017 (UTC)

Drift speed

The section on drift speed suggests that the speed of sound is faster than the speed of gas molecules. From Maxwell–Boltzmann distribution, the mean speed of nitrogen molecules is 422 m/s, a little faster than the speed of sound in air or nitrogen gas. Gah4 (talk) 10:48, 10 January 2017 (UTC)

Holes

There is the statement In other materials, notably the semiconductors, the charge carriers can be positive or negative, depending on the dopant used. which seems to suggest that holes only exist in semiconductors. Many metals have hole bands, and in fact Aluminium, a metal widely used for power transmission, has a large fraction of its conduction in hole bands. Gah4 (talk) 10:21, 10 January 2017 (UTC)

I see that the clause about dopant suggests only dopable materials. Perhaps the sentence can be rewritten "In other materials, notably the semiconductors (depending on the dopant used), the charge carriers can be positive or negative." Or maybe it needs to be two sentences with the second sentence adding the information that the charge carrier type in semiconductors depends on the dopant. Never the less, it is interesting that aluminium has considerable hole conduction. If you have a reliable source, I think it would be a good addition to the article.Constant314 (talk) 19:03, 10 January 2017 (UTC)

The dopant is a distraction here. Intrinsic (ie undoped) semiconductor materials also have conduction band electrons and valence band holes both taking part in conduction. What the dopant does is create more of them, usually biased towards one or the other to create p-type or n-type materials. But another point is that holes are not real particles, they are an absence of an electron. The current is still being carried by electrons in reality. The virtual holes are just an analytical convenience. A better example of positive charge carriers is the cations in an electrolyte. SpinningSpark 19:29, 10 January 2017 (UTC)

Holes come from the quantum mechanics of band theory. Both the Hot-point_probe and positive hall coefficient in some materials show the need for holes in explaining conduction in solids. The quantum mechanics rules on indistinguishability don't allow one to track individual electrons through a conductor. Gah4 (talk) 23:42, 17 January 2017 (UTC)

The band structure of aluminium, commonly used in electric power transmission, is described by Ashcroft and Mermin.

References

Hydronium

The electrolytes section mentions proton motion, but not Hydronium. As well as I know it, in most cases hydronium ions move. According to its article, there are solids with hydronium conduction. Gah4 (talk) 22:51, 12 May 2017 (UTC)

Conduction Mechanism

A mention that current in wires is a start-stop motion of millions and millions of conduction band (or, free) electrons everywhere within with a drift superimposed should be made. In a simple electric circuit comprising battery, wires and a bulb, direct current in the steady-state is due to an electric field set up by a gradient in surface charge density. The drift speed of the free electrons usually does not exceed about 1/200 the speed of light and is not greater than a few meters per hour. It is the change in the electric field (from circuit OFF to ON,)which is uniform in the wires and the bulb filament (stronger field than in the wires) made by a surface charge gradient, occurs at nearly the speed of light.

References [19] Ruth W. Chabay and Bruce A. Sherwood, Matter and Interactions Vol II, Electric and Magnetic Interactions, John Wiley, 2010

[20] Hermann Härtel, “Voltage - a Basic Term in Electricity Shortcomings of the traditional approach and new ideas for improvement”, Institute for Theoretical Physics and Astrophysic, University Kiel, 2008. http://www1.astrophysik.uni-kiel.de/~hhaertel/PUB/voltage_girep.pdf should be included. 117.213.227.68 (talk) 11:07, 22 August 2017 (UTC)

Current convention

Positive flow is a convention for describing the direction of current. Often it is the opposite of the actual current / movement of charges. The article is confusing as it refers to it as being current; I tried clarifying by referring to it as a visualization and was reverted. Not saying that my method was the best, but this should get clarified. Sincerely, North8000 (talk) 03:13, 24 January 2018 (UTC)

It gets more complicated with quantum mechanics, which doesn't allow one to track individual identical particles. But otherwise, it is the convention and doesn't require any visualization. Gah4 (talk) 03:30, 24 January 2018 (UTC)

There is already an entire section devoted to the meaning of conventional current.Constant314 (talk) 03:31, 24 January 2018 (UTC)

I still stand by my first post but it's a minor issue either way and I don't intend to go any further on the point. Sincerely, North8000 (talk) 13:45, 24 January 2018 (UTC)

strong disinformation!

"The high speed of electromagnetic waves is roughly analogous to the speed of sound in a gas (these waves move through the medium much faster than any individual particles do)"

Speed of a sonic wave in a gas is about 1/2 of the molecules average speed.

It could be improved. It means the speed of EM waves is much greater than the drift velocity of the electrons. The speed of sound is usually greater than the bulk motion of air. Constant314 (talk) 03:39, 29 January 2018 (UTC)

Symbol inconsistency

The 'Symbol' paragraph says the correct symbol is I, but the simple circuit diagram in the upper left of the article uses lower case i. Which is it? Is it either?

Both are correct, but many authors use lower case i to mean a current that is a function of time and upper case I for a constant or a phasor that is a function of frequency. Constant314 (talk) 14:56, 28 February 2018 (UTC)

fundamental unit

ampere is listed as one of the fundamental units, yet it's defined in terms of the coulomb, which is listed as a derived unit. a coulomb is defined either in terms of the mole (electric charge of a small fraction of a mole of protons / electrons) or in terms of the ampere, so it's clearly not fundamental. how can the ampere be fundamental, then? — Preceding unsigned comment added by 2601:584:300:FDF0:7C33:42A9:4679:E74D (talk) 02:41, 4 February 2018 (UTC)

It is just loose language. The ampere is fundamental. It is the coulomb that is derived; it is defined as 1 ampere x 1 second. The ampere is chosen because it is easier to measure and reproduce than a coulomb. Constant314 (talk) 03:34, 4 February 2018 (UTC)

So we don't really need a Coulomb, and could use Ampere second instead. Note that batteries are commonly described in terms of mA h, or, for larger ones, A h, mostly because that is closer to the way they are used. Even though electrostatic seems more fundamental, SI units are defined in magnetostatic terms. Gah4 (talk) 21:58, 5 February 2018 (UTC)

The battery terms have a different meaning even though the units are the same. North8000 (talk) 01:40, 6 February 2018 (UTC)

Well, it isn't so fundamentally different, though the scaling factor is a little more convenient. 1 mA h is 3.6 A s or 3.6 C. More often, one wants the time in hours. Reminds me of the story of the cop who stops a lady (it is always a lady) for speeding, telling her she was going 60 miles/hour. She says that can't be, as she has only been driving ten minutes. A battery rated at 1000 mA h likely can give 1000ma for an hour, but likely not 3600A for 1 second. Speed limits in feet/second or in metric countries meters/second would have values about the right size, but the conversion to useful units isn't so easy. (44 feet/s is 30 miles/hour). On the other hand, the Volt Ampere, used in AC circuits, is fundamentally different from the watt. More interesting are the units used for rechargeable batteries. The unit C, which is not Coulomb, but instead capacity (no relation to capacitor). For a 1000mA h battery, C is 1000mA, so a charge rate of 0.1C is 100mA. For NiCd batteries, 0.1C is the current that one can use continuously, without knowing the charge state. All for convenience, and doesn't make sense dimensionally at all. There must be some history, but I don't know it. Gah4 (talk) 16:10, 2 March 2018 (UTC)

Thanks for that interesting info. What I meant is that the terms very different meanings in their context. One is purely purely a unit of electrical charge. The other is an indirect indicator of the power output capability of an electrochemical system under to a certain testing criteria, which includes a practically constant voltage, thus allowing indicating it using "charge" type units. North8000 (talk) 17:07, 2 March 2018 (UTC)

For currents that aren't too large or too small, the capacity should be close to $\int I(t)dt$, which has units of charge. Gah4 (talk) 20:13, 2 March 2018 (UTC)

Yes. I think that it more a matter of the common meaning of the term "electric charge". Usually it refers to an electric charge situation, such as a capacitor. But it's units are also that measure of a battery, and that measure is also a description of how much total electric charge it can deliver under a particular set of testing rules.

Yes, we do not really need the Coulomb, but it is a useful unit that has a solid physical definition: it is the charge delivered by a current of a amp in one second.Constant314 (talk) 00:09, 3 March 2018 (UTC)

Conduction mechanism in superconductors

In the conduction mechanism section all entries but the superconductor one describes the _mechanisms_ of conduction. I suggest changing the superconductor entry to follow the pattern of the rest.

Example (with adapted text taken from superconductivity article):

Superconductivity is a phenomenon of exactly zero electrical resistance and expulsion of magnetic fields occurring in certain materials when cooled below a characteristic critical temperature. In a normal conductor an electric current may be visualized as a fluid of electrons moving across a heavy ionic lattice, with the electrons constantly colliding with the ions of the lattice this results in dissipated energy. In a conventional superconductor the current instead consists of bound pairs of electrons known as Cooper pairs behaving as a superfluid. As the current is not scattered by the ions of the lattice it flows without energy dissipation. — Preceding unsigned comment added by 2.248.146.217 (talk) 14:28, 3 March 2018 (UTC)

The link to superconductivity explains it well. As there is no article on semiconductivity, (it is a link to semiconductor) the semiconductor section explains it in much detail. I suppose one sentence on Cooper pairs and superfluidity wouldn't be bad, though. Gah4 (talk) 19:26, 2 May 2018 (UTC)

Vector

As far as I know, electric current should be considered a vector quantity. Often enough, that can be ignored, as it can, for example, in cases of falling objects with no transverse component. When considering the magnetic field, current is a vector, even when contained in a wire. In some cases, it is necessary to consider the distribution of current inside a wire. In bulk, where it is actually current density, one often still speaks of electric current. Gah4 (talk) 19:13, 2 May 2018 (UTC)

Current is the surface integral of current density. The dot product of current density and unit normal at each surface element is integrated, so I get that current is not a three dimensional vector, but it is signed and is a perfectly good one dimensional vector. In a circuit, the surface is usually the cross section of a wire. The wire can be bent in a very convoluted way, but the current remains the same. I would like to hear how it is a tensor in some sense other than the trivial sense that all vectors can be treated as tensors. I don't like to have a section that basically says here is a fact that only clever people know without explaining it. As it is, it is a useful fact (if it is a fact) only to people who already know the fact. So, if there is going to be a statement that current is not a vector but is a tensor, then it should be fleshed out enough so that it is meaningful to people who do not already know what it means. Constant314 (talk) 20:17, 2 May 2018 (UTC)

Yes, I don't know of it being a tensor, either. Some things that are scalar in the easy approximation are tensor when done right. Conductivity is one. There is Four-current which should probably be linked from here. Electromagnetic field is a four-tensor in special relativity, but that doesn't make it obvious to me that current should be. But for much of electronics, current can be considered a scalar, as close enough. Gah4 (talk) 21:10, 2 May 2018 (UTC)

A couple of points. As a starting point, with "current" we're talking about a word, and we need to be significantly dealing with the common meanings of the term. Also, more powerful mathematical visualization tools are merely tools which are used/selected only when they are needed, not inherent realities of the the subject. The common mathematical meaning of current is a numerical vale. Even calling it a scalar is putting it in the context of a particular more powerful specialized tool set which is usually not used or needed. So IMO such things should be kept in perspective.....in some specialized area in the body in the article. North8000 (talk) 21:36, 2 May 2018 (UTC)

Respected Wikipedians,I am a Student of Science in High School.I researched about it and found that Electric Current is called a Scalar quantity because it does not follow law of parallegram for vector addition though it has direction.In smaller classes it is regarded is scalar.But when you study in higher classes you will get to know that both vectors and Scalars are special type of Tensor.Thankyou..! Binamra Deb (talk) 08:46, 4 May 2018 (UTC)

So we can call it a Tensor...I think we should add it in a Seperate part in the article. Binamra Deb (talk) 08:47, 4 May 2018 (UTC)

I think that this calls for a reliable source and I also think that it is too technical for this article. Conductivity as a tensor would be fine on the conductivity article because it is easy to show a concrete example. If some one has a concrete example of current showing tensor behavior, please share it. Constant314 (talk) 10:28, 4 May 2018 (UTC)

Current is not a vector quantity, but it's something that can be represented by vectors, as it has an intensity and a direction, a starting point, and a ending point. But it's a scalar quantity: see explanations here: https://www.quora.com/Is-current-a-scalar-or-a-vector-quantity — Preceding unsigned comment added by 80.215.6.79 (talk) 16:22, 29 September 2018 (UTC)

Positive Hall coefficient

I recently added this to Talk:Hall effect: It seems that Beryllium, Cadmium, Cerium, Iron, Molybdenum, Tungsten, and a few other metals, have positive Hall coefficients. With one valence electron, it is most likely to have a half full band. (Complicated by crystal symmetry and such, but usually ...) With two valence electrons, it could be a full band (insulator), or two bands more and less than half full. Note also that the metals with positive Hall coefficient also tend to have high resistivity. With one hole and one electron band, the sign will depend on which one is more, and which one is less, than half full, and the mobilities in each. Aluminum has three valance electrons, which can partially fill three bands. So, some hole and some electron bands, and they change with magnetic field. At high magnetic field, Hc of Al goes positive, but is always the result of both holes and electrons. Gah4 (talk) 18:21, 12 April 2018 (UTC)

Yes metals have hole bands, though it takes more than the simplest theory of conduction to show it. The positive Hall coefficient of them makes it easy to test. Gah4 (talk) 21:04, 12 November 2018 (UTC)

But don't metals have a positive temperature coefficient of resistance, which is the reverse of the negative TCR associated with hole generation? As always, a citation would be great - one accessible on the Net would be ideal! I picked up "Electrical Conduction in Solids: An Introduction" by Daniel D Pollock, but it's *so* introductory it doesn't mention Hall effect at all. Oh, wait, here it is, finally on page 106 " The transition elements ...., atoms with incompleletly filled outer d and s bands, also show reasonably good metallic behaviors. Here, the holes may also enter into the conduction process." But aluminum isn't a transition element? --Wtshymanski (talk) 00:45, 13 November 2018 (UTC)

The positive temperature coefficient is for semiconductors, where carrier density, holes and electrons, increases with temperature, as they are thermally excited from the valence to conduction band. Metals have partially full bands. If a band is less than half full, it has electrons, if more than half full, holes. My usual reference is Ashcroft and Mermin, which has a picture of the Fermi surface of Aluminum. The Hall coefficient for Al goes positive at high magnetic fields, as the bands shift. With two electrons/atom, you can fill a band (spin up and spin down), or form two partially full bands. The exact levels and mobility determine whether electrons or holes win. With more electrons per atom, more partially full bands are possible. Gah4 (talk) 01:42, 13 November 2018 (UTC)

Metals have a positive temperature coefficient, it is one of their defining parameters. It is nicely demonstrated by your humble tungsten filament light bulb. The filament temperature is approximately 10 times the resistance when hot (~2,700K) compared with cold (293K). Non-metals have a negative temperature coefficient. Again demonstrated nicely by a carbon filament lightbulb where the resistance is much higher when cold than when hot. (by about 15 times). DocFergus (talk) 18:44, 13 November 2018 (UTC)

It depends on resistivity vs. conductivity, but either way it is opposite for metals and semiconductors, and not on holes vs. electrons. Google for holes in metals gets plenty of hits, along with ones related to drilling and punching. Gah4 (talk) 22:01, 13 November 2018 (UTC)

Resistivity is simply the inverse of conductivity and there can be no other dependency. The problem with 'hole conduction' explanations is that holes don't really move. It is what fills them that moves. Hole conduction is frequently employed as a convenient way of explaining away certain behaviours without having to resort to more complex and harder to understand explanations. The classic (and possibly original) case is explaining NPN bipolar transistors using electron conduction but then resorting to hole conduction for the PNP transistor simply because the explanation is, more or less, the same rather than going to the trouble of explaining how they really work with electron conduction. DocFergus (talk) 12:56, 14 November 2018 (UTC)

A full band causes no conduction, with as many electrons moving one way as the other. In the case of hole bands, it is actually electrons with a negative effective mass that move. It is easier to think about objects with positive effective mass and positive charge. In any case, some metals do have a positive Hall coefficient, which means positive charge carriers. The band theory explanation of metals with more than one valence electron per atom, has more than on partially full band. Often that means both electron and hole bands, depending on the shape of each band. You need both electrons and holes to explain bipolar transistors, electrons to explain n-channel FETs and holes to explain p-channel ones. Gah4 (talk) 17:45, 14 November 2018 (UTC)

French phrase

Intensité du courant, not intensité de courant. Du is the contraction for de+le, le is needed in French grammar. — Preceding unsigned comment added by 80.215.6.79 (talk) 16:16, 29 September 2018 (UTC)

 Done: You are correct. DocFergus (talk) 13:48, 15 November 2018 (UTC)