Talk:Capacitor/Archive 2

Archive 1

Archive 2

Archive 3

Archive 4

Trimpots

A previous version of this page referred to small variable capacitors "trimpots". AFAIK, trimpot is short for "trimming potentiometer", a type of small variable resistor you turn with a screwdriver. A quick Google search showed that my usage is certainly common, so I deleted that reference. -- Tim

Yes, trimpots are resistors. There are trimmer capacitors, though. - Omegatron

Yes,there are trimmer capacitors. They are called trimmer caps, or just trimmers for short. THey are never called trimpots.--Light current 18:43, 17 September 2005 (UTC)

Biological capacitors

We need to add the technical use of "capacitor" in biology. -- Anon.

And what is this technical use? - Omegatron

Charge on plates or insulator?

It isn't always recognised that the charge stored in a capcitor is not stored on the plates but on the surface of the insulator or dielectric.

Is this correct? Since you can have air capacitors or vacuum capacitors I can't see how this is the case. I always understood that the charge was the electrons pulled towards the other plate, and therefore on the surface of the plate. I only studied Electronics and Physics to A-level so I will wait for an expert to verify rather than changing the article myself. -- Chris Q 14:14 Feb 18, 2003 (UTC)

I changed it. It is not really a contrast: The charge is at the boundary. - Patrick 14:31 Feb 18, 2003 (UTC)

It is possible to experimentally prove that the charge is not on the plates. It can easily be done in a system where you create the charged capacitor, remove the plates, short circuit them to demonstrate no electrical energy and then replace them on the insulator. Yes you can have air capacitors but if the air was stirred the charge would dissipate. Vacuum capacitors store the charge on the glass insulator with the vacuum providing a high resistance to electrical discharge between the two opposing chargesRjstott

??? How do you remove the plates from the system without removing the dielectric? Stirring the air does not discharge an air cap, except maybe the charge that is transferred through moisture from one plate to the other. Air capacitors are used commonly in radio. What glass insulator? Wouldn't that make it a glass-dielectric capacitor? - Omegatron

I've always thought that the energy was stored in the dielectric (which actually can be true for a vacuum, the energy density is 0.5*epsilon*E^2), but not the charge - the existence of vacuum capacitors should illustrate that clearly. What does happen for a dielectric is that the charge in the dielectric shifts slightly, still giving a net neutral charge for the bulk of the dielectric, but partially cancelling the free charge at the surface so that one can fit more free charge for the same voltage.

The "energy" (meaning potential energy) is "stored" in the distance of the charge away from the voltage reference. Potential energy doesn't really exist, but true to its name, it is energy that potentially could exist if the charges were allowed to move accross toward that voltage reference. Energy can't be "stored" in a vaccuum unless you're talking about EM or something, but I am interested in the equation you mentioned 0.5*epsilon*E^2 - what is that? Fresheneesz 18:02, 20 November 2005 (UTC)

Might not be entirely relevant to the article, as the overview is correct as it stands, but it may be important to keep in mind. StuartH 05:36, 9 Jun 2004 (UTC)

http://www.amasci.com/emotor/cap1.html

I just read Bill Beaty's article at the above URL. It is excellent, and should be read by all contributors to this Wikipedia article. In fact, I wish we could steal the whole thing word-for-word. Can we hire Bill to write for us? I think our article has a slight touch of the 'physicist's capacitor' versus the 'engineer's capacitor' problem.

By the way, Bill's article explains why the statement "It is possible to experimentally prove that the charge is not on the plates." above is wrong. -- Heron 14:36, 10 Jul 2004 (UTC)

seriously. has anyone ever tried inviting him to wikipedia? - Omegatron 20:20, Jul 10, 2004 (UTC)

I've been here for a couple of years, mostly wreaking havoc on entries such as Electricity, Conduction, Charge, etc. --Wjbeaty 01:25, Dec 28, 2004 (UTC)

This would be pretty easily proved by building two identical jars, charging one, and swapping components. Which one has the charge now? "The charge is on the dielectric", according to the Leyden jar article, which I have moved to the talk page. - Omegatron 00:33, May 31, 2005 (UTC)

Oh. I see that it is not so easy because of the corona effect. - Omegatron 00:37, May 31, 2005 (UTC)

Interesting, I was not aware that this experiment had been done in the way described and perhaps the explanation has some merit. However, the way I saw it done involved two large flat plates and a large flat dialectric where the separation was done by moving the plates perpendicularly away from the dielectric rather than horizontally. No corona effect?--Rjstott 03:46, 12 September 2005 (UTC)

Stored charge or energy?

Is it true that "a capacitor stores electric charge", as the article claims? I think it's more accurate to say that a capacitor stores energy by redistributing its internal electric charges to create an internal electric field. The electrons and protons are there regardless of the capacitor's state of charge, but in the case of a discharged capacitor the opposite charges are mixed in equal concentrations on both plates. In fact, the word "charged" in this context means "full of energy", not "full of electric charge". If a capacitor really stored electric charge, the whole component would become either positive or negative, and the charge would soon leak away to the environment.

Perhaps I'm just splitting hairs. I'll wait for comments before I make any changes to the article. -- Heron

I rephrased it. Indeed the plates get "full of electric charge". The energy is a consequence, not the primary thing. And you make it sound as if the charge moves internally, but it moves externally through the circuit from one plate to the other. - Patrick 09:53, 3 Sep 2003 (UTC)

Patrick, I dont know if youre still here, but what you have said in the above post is most important. Charge separation occurs via the external circuit not across the plates. So you dont need to postulate any thing passing between the plates. We know charge cannot pass, but does any form of current really need to pass to charge the capacitor?? --Light current 01:26, 12 September 2005 (UTC)

Triboelectricity

I don't see what triboelectricity has to do with capacitors, besides being a possible source of charge to charge one up. Yet there is this paragraph in the article:

Triboelectricity is an important associated phenemonon. This is the generation of electricity by rubbing an insulator. The ancient Greeks experimented with this. Not all capacitors are intended by man; as lightning will attest. Taking the carbon black out of automobile tires has improved their functioning as a dielectric, as any (prob. elder) one who has been shocked at the gas pump can attest. Electrodynamics is even of interest to astronomers. Triboelectricity and magnetics (associated with inductors) are the two possible ways to directly convert mechanial energy into electrical energy.

Are they trying to say that the two separated surfaces are a capacitor? Then any two completely irregular, non conducting surfaces would be a capacitor, as long as there was a difference in charge between them. - Omegatron 18:38, Jun 8, 2004 (UTC)

Recent edits by 24.12.159.248

248, I've been watching your edits (as 128.12.178.70) and I want you to encourage you to add information. It's your organization and style that I think could use some work. Some points:

• Stay on topic in the articles and sections that you modify. If you wander into a side topic, and then a side topic of that topic, that's not good. Try to work your parenthetical remarks into the main text; if you can't do this, perhaps the remark is too far off-topic.
• Avoid replicating information that is in other articles.
• Use complete sentences and avoid informal language.
• When you use pronouns, make sure that the antecedents are clear.
• Don't use first-person or second-person references. Wikipedia is a collective effort with open access.
• Remember that the audience includes people who know nothing about the article subject, and that WP cannot hope to be a substitute for formal engineering training. Therefore focus on fundamentals and hard facts before engineering practice.
• Please, no jokes. Since the audience does include people who know nothing about the subject at hand, your well-intended, light-hearted comments are just as likely to confuse as to entertain.

Again, I want to encourage you to add relevant information. Just make sure that it's added in such a way as to maximize its usefulness to readers. Gazpacho 02:43, 9 Jun 2004 (UTC)

Some recent edits

In 'information theoretic' terms capacitors are used both to "store" and "destroy" information. They can be used to store binary or voltage information, in digital memories or switched-capacitor circuits. They are also used to destroy information, when used to shunt away high frequencies in filters. Even when it is used to store information, it is destroying other information, for example, when it is used as the storage element in a DRAM, one duty of the capacitor is to 'forget' when the bit was written. When they were used in 'bucket brigade' delay lines, they also functioned as an Low Pass Filter.

What is "information theoretic"? How does a capacitor destroy information? A capacitor can store information either in the form of an analog voltage (switched-capacitor filters) or a digital voltage (DRAM). In the DRAM example, the capacitor is not destroying information, it is simply storing a new value. You could say perhaps that the resistor shorting the capacitor charge to ground is destroying the information in the capacitor, or that the memory chip itself is destroying the information by writing over it with something else, but the capacitor isn't doing it, and I don't understand the relevance anyway.

Capacitors exploit electrostatics, inductors, electrodynamics. This leads to a 'symmetry breakdown.' Yes, inductors can be thought of as being 'inverse capacitors,' but there is no 'transformer (i.e. proximity) effect' associated with capacitors. There is no transformer-like effect associated with capacitors.

Capacitors exploit electrostatics, and have parasitic, unwanted inductance, and I suppose are electrodynamic. Can you please explain in more detail why inductors and capacitors are not duals? What is the "transformer effect"? Capacitors can be used as coupling devices in a way roughly similar to transformers.

Intercell (capacitive) nerve connections limit athletic reaction time.

What does this have to do with parasitic capacitance?

a property of the ideal current amp) for speed, given the same Qdiss. Quie

What does Qdiss stand for? please elaborate. - Omegatron 07:09, Jul 10, 2004 (UTC)

----

I fixed most of the points that you questioned above, Omegatron. (They weren't my points, by the way.) Next, I consulted The Penguin Dictionary of Electronics (ISBN 0140511873), which gave me a much clearer picture of how capacitors work, and helped explain the "capacitor/inductor dualism" thing.

The dictionary first defines capacitance as the ability to store charge, which for an isolated conductor is C = Q/V, where V is the voltage change after the addition of a charge Q. It then mentions that two such conductors make a capacitor, and that the capacitance of this thing is the ratio of the charge on either conductor to the voltage difference between them. Note that the isolated conductor has capacitance, but is not a capacitor. I interpret all this to mean that the charge (and now I am confident enough to call it charge, and not energy) stored in a capacitor is held on the plates: +Q on one plate and -Q on the other. The "dismantling a Leyden jar" experiment, which would appear to contradict this, can be explained by corona discharge, as Bill Beaty does in his article referred to above. If this is true, we can stop beating about the bush and proudly state that a capacitor stores charge (or, more accurately, that it stores two equal but opposite charges). The stuff about polarisation of the atoms in the dielectric explains dielectric losses, but has nothing to do with why a capacitor is a capacitor.

I now also understand a bit better the symmetry between capacitors and inductors, and it is neater than our article presently admits. Both devices allow some of their field to leak out, although the leakage is more noticeable with inductors than with capacitors. If two inductors become magnetically coupled, then they make a transformer. The degree of coupling is called mutual inductance, which is defined as the voltage in one inductor caused by a changing current in the other. Similarly, two capacitors can be electrostatically coupled, a fact which is sometimes overlooked, although you (Omegatron) alluded to it. The degree of coupling is called - guess what - mutual capacitance, which is defined (thanks to my Penguin dictionary) as the current in one capacitor caused by a changing voltage in the other. A quick Google for "electrostatic transformer" finds lots of hits related to particle detectors, so it seems that this effect has a practical use, but not one that many electrical engineers would be familiar with.

The symmetry argument breaks down when you try to imagine the dual of the 'isolated conductor'. I think this is related to the fact that magnetic monopoles do not exist. -- Heron 21:21, 10 Jul 2004 (UTC)

Thanks. I didn't know that an object by itself in empty space could have a capacitance. Here is another link explaining this: http://www.qprox.com/background/capacitance.php - Omegatron 23:17, Jul 10, 2004 (UTC)

Mutual capacitance

Oh dear. That article contradicts my Penguin Dictionary's definition of mutual capacitance. So do many other web pages. My dictionary said that mutual capacitance was the interaction of two capacitors, but it seems that it is really the interaction of any two charged conductors. A capacitor is a special case of mutual capacitance in which the two objects are brought close together, so that the electric field is confined mostly to the small volume of space between them and does not affect other nearby objects. -- Heron 11:12, 11 Jul 2004 (UTC)

Oh dear. I don't know the answer.

I would still like an explanation of how capacitors destroy information. "Information theoretic" was probably supposed to link to information theory, and I have some familiarity with it, but i still don't understand what the author was trying to say. - Omegatron 19:34, Jul 16, 2004 (UTC)

It's incorrect anyway. Lossless filters, involving only capacitors and inductors, either reflect energy or transmit it. A lossless low-pass filter doesn't destroy high frequency information, it reflects it back to where it came from. Resistors on the other hand dissipate signals as heat, increasing the disorder of the system, thereby creating information. Nothing destroys information. -- Tim Starling 01:18, Nov 30, 2004 (UTC)

Capacitor vs Capacitance

Although I find Capacitor to be a very good article, it deals with both the physical objects (capacitors) and the physical quantity (capacitance). This causes issues for the categorisation of the article. For clarity, I would prefer to split the current article into separate (but linked) articles on each aspect. Does anyone have any objection to this, please? Ian Cairns 00:32, 14 Nov 2004 (UTC)

RF stubs

I quote from "types of capacitor":

stubs: In RF circuits, a length of transmission line less than a quarter-wave, that is shorted at the end, or a length greater than a quarter-wave left open, has the electrical properties of a capacitor.

I'm not an RF engineer, but I'm pretty sure this is the wrong way around (ie both examples would behave inductively). Could someone with more relevent knowledge make the edit if it is required?

Field-theoretic items

Since a capacitor is inherently a "lumped" circuit element, perhaps the lengthy Maxwellian discussion could be moved elsewhere? All that grad div and curl stuff is intimidating and everything after "forcing function" could be removed with a useful shortening effect to this article. An observation that practical capacitors have all three elements of capacitance, inductance and resistance, and a note that at high frequencies it's no longer useful to use the lumped circuit approximation, should be all that's required in this article. --Wtshymanski 17:53, 1 Jan 2005 (UTC)

Edits similar to inductors

It would be nice if inductors, capacitors, and resistors followed a similar structure. Any of the previous suggestions are OK with me as long as there is consistency. I like the idea of physics first, then electrical, practical etc. I tried to add some of the same content found in inductor article, e.g. energy. I haven't looked, but this could all be tied into KVL and KCL circuit analysis at some point. Just my $0.02 - Madhu

I said the same thing when I first saw the articles, but never finished it. Be bold and do it. - Omegatron 05:12, Feb 17, 2005 (UTC)

Oh. For some dumb reason capacitance is a separate article from capacitor. So some of what you are adding might be in the other already. - Omegatron 05:15, Feb 17, 2005 (UTC)

Metal plates

Someone says not all capacitor plates are metal. I'd appreciate a citation? News to me. I'm taking it out for now. --Wtshymanski 04:28, 15 Apr 2005 (UTC)

It may be news to you, but capacitors using conductive plastic plates have been available for quite a few years. There are those that use aluminized mylar (sort of semi-metallic), but there are also those that use conductive polymers without coatings.

Cool. I've never heard of those. Can you show an example datasheet? Please explain this in the article. - Omegatron 12:47, Apr 16, 2005 (UTC)

Agreed, I'd like to know more; someone has changed it again but not listed a reference. Like I said, news to me. I can't see the utility - conductive plastics are very poor conductors. Who makes these? --Wtshymanski 14:45, 16 Apr 2005 (UTC)

Um... Supercapacitors? ultracapacitors? Last I heard, carbon was not a metal. Also, I think I recall seeing "Plastic capacitors" in the digikey catalog. Search google for solid polymer aluminum capacitors, or just "conductive polymer" +capacitors --Wjbeaty 21:57, Apr 17, 2005 (UTC)

I'd forgotten about supercapacitors. And the Kemet paper at http://www.kemet.com/kemet/web/homepage/kfbk3.nsf/vaFeedbackFAQ/134ECF096F57820885256F72006669BA/$file/1999%20CARTS_Replacing_MnO2.PDF shows that even tantalum capacitors have a non-metallic anode plate. The ignition hazard of tantalum capacitors is also something I'd never read about before. --Wtshymanski 22:23, 17 Apr 2005 (UTC)

condenser

called a condenser because it "condenses" more charge into the same space? for instance, applying a voltage to two metal plates a meter apart would only imbalance the charge a tiny bit. placing them very close together and then applying the voltage allows much more charge imbalance in the same volume. as far as electrons are concerned, they are now "condensed" tighter together. more are able to be "stored" (and vice versa for holes, of course). - Omegatron 02:14, May 21, 2005 (UTC)

I think you are right. This article on Ben Franklin gives the same explanation. Also, here are some citations from the OED:

I had rather call it a condenser of electricity..using a word which expresses at once the reason and cause of the phenomenon. -- Volta in Phil. Trans. LXXII. App. 8, 1782

and

Accumulators are sometimes called Condensers, but I prefer to restrict the term ‘condenser’ to an instrument which is used not to hold electricity but to increase its superficial density. -- Maxwell Electr. & Magn. I. 50, 1881

and Abraham Bennet wrote to the Royal Society in 1787 thus:

The labours of M. VOLTA have been very successful on this subject by the application of his condenser (as he terms it), which, by means of a thin coated electric, is capable of receiving a greater quantity of electrical fluid than a common insulated conductor... (Philosophical Transactions V77 (1787) pages 288-296, found at [1])

which corroborates Volta's claim to have invented the term (which he probably translated from the Italian condensatore). --Heron 11:09, 21 May 2005 (UTC)

Excellent work! Thanks. We should include this in the article, of course. - Omegatron 16:08, May 21, 2005 (UTC)

I have done so. Now I want to know more about those "Ancient Greeks". Which ones, exactly? --Heron 20:10, 21 May 2005 (UTC)

I can't find an etymology of the word capacitor. Most non-English languages use a variant of condenser or condensatore. I wonder who the first was to use capacitor. This is the best I can find and I don't trust it:

The name "capacitor" was given in the US due to its capacity for charging electricity. When capacitors were introduced to Japan, the English word "capacitor" was translated as "chikudenki," which means a component that can condense and store electricity. Later, people in Japan thought it was called condenser in the US when they retranslated it into English. That is the reason the electric component called capacitor in the US is still called condenser in Japan. Moreover, in another theory it used to be called the "condenser" in the world, but recently there is also an opinion of having came to be called "capacitor". - Omegatron 13:38, May 22, 2005 (UTC)

Hmm. That sounds like an answer to the question "Why do the Japanese still call them condensers?"

The OED doesn't record the exact moment of conception, but it has a quote from the 1922 BSI Glossary of Terms in Electrical Engineering that describes 'capacitor' as a 'new term' and recommends its use to avoid confusion with the steam 'condenser'. The OED gives the etymology as from 'capacity', which meant 'capacitance' as early as 1777 (in Tiberius Cavallo, A complete treatise of electricity in theory and practice). --Heron 17:17, 22 May 2005 (UTC)

Definition of capacitance in words

Capacitance is a measure of the amount of charge stored (separated?) in a capacitor for a given voltage across the capacitor. That is, for a given V, Q is proportional to C. The original wording implied that for a given Q, V is proportional to C when in fact V is inversely proportional to C. Alfred Centauri 01:21, 26 May 2005 (UTC)

Transfer Function

From the "In electric circuits" section:

"The transfer function for an ideal capacitor can be written as a differential equation in time domain"

A transfer function lives in the frequency domain and so is not the appropriate term here. Also, the use of the term differential equation is a stretch. Although the equation does involve the derivative of v(t), it does not involve v(t) itself or any other derivatives of v(t) thus placing zero constraints on the function v(t) other than that its derivative must exist. I've changed the wording to a more standard form:

"For an ideal capacitor, the capacitor current is proportional to the time rate of change of the voltage across the capacitor where the constant of proportionality is the capacitance, C:"

Alfred Centauri 02:39, 26 May 2005 (UTC)

not exactly

"Because each plate stores an equal but opposite charge, the total charge in the device is always zero."

Not exactly.  :-) Scuff your feet across the floor and then touch one side of a capacitor which is otherwise insulated from everything else. That side of the capacitor will now have a net charge. Whether we should actually include this or not, I don't know. It probably confuses understanding more than anything... Electricity can flow in things that are not circuits, though, which is probably an important thought process that is being lost in our age... Would learning about the fundamentals of charged objects help or hinder understanding of circuits? I don't know. - Omegatron 00:04, May 28, 2005 (UTC)

I wouldn't include it since a capacitor is, by definition, a two terminal circuit element used in electric circuits where, by definition, charge is made to flow along a closed path (circuit). Let's face it, if you scuff your feet and touch the chassis of an isolated, battery powered circuit, the entire circuit has net charge. In this case, we can talk about the capacitance of the entire circuit. Perhaps this kind of stuff would be better in the Capacitance article, which has, IMHO, a lot of material related to Capacitors that doesn't belong there. Alfred Centauri 16:53, 28 May 2005 (UTC)

Well, technically a capacitor is any two conductive objects separated by a dielectric. A coax cable is a capacitor, for instance. Two pins of an IC form a parasitic capacitor, and so on.

But, that's exactly my point - a capacitor is a two-terminal device that is charged by moving electrons from one plate (conductor) to the other via an external circuit. On another note, would you agree that the term capacitor refers to, in practice, an intentional capacitor and not the inescapable and ubiquitous parasitic capacitors found in all electronic components (including resistors, inductors, p-n junctions, etc. etc.)? Alfred Centauri 17:58, 29 May 2005 (UTC)

Yes, "capacitor" usually refers to intentional components. It also refers to parasitic components as part of a circuit quite often. Rarely does it refer to the abstract capacitance between two completely isolated conductive objects. That is usually just referred to as "capacitance", if you're talking about the two words themselves. Obviously they're both talking about the same thing. - Omegatron 20:50, May 29, 2005 (UTC)

Hmmm... OK. However, I personally do prefer to use the term capacitor to refer to the device and parasitic capacitance to refer to those uninvited guests and capacitance to the physical phenomena due to the electric field. Alfred Centauri 01:55, 30 May 2005 (UTC)

Yeah. That's probably how we should keep the articles, too. - Omegatron 02:30, May 30, 2005 (UTC)

Yes, you could touch and charge an entire circuit, but any capacitors in the circuit would isolate the charge, inductors would resist the sudden charge imbalance, etc. The kind of stuff that causes noise in signal processing gear from triboelectric effect in cables and so on. If you did scuff your feet and touch one side of an otherwise floating cap, you could then discharge the cap and do (a small amount of) work, since there is a charge imbalance across its plates. And, if my understanding is correct, you can fit more charge on one side of a capacitor than you could on the same piece of metal if the capacitor were disassembled. It's not completely trivial.

Yeah, it probably should be in the capacitance article instead, maybe with a little "(see capacitance for more details)". - Omegatron 20:51, May 28, 2005 (UTC)

I don't quite understand what you are getting at in your first sentence above. Can you elaborate? I'm not sure about being able to store more charge on one plate of an assembled capacitor versus a plate in isolation. Do you have any further info on this? Finally, when you say 'discharge the cap', do you mean to discharge through an external circuit connected across the cap or to a discharge to ground the lead that you touched? Alfred Centauri 17:58, 29 May 2005 (UTC)

Sure. I was just saying that you can charge a floating circuit with a static charge, but the entire circuit doesn't charge at once. Your injection of electrons or holes into the circuit causes currents to flow, etc. Any section of the circuit that is completely isolated with capacitors will not become charged, too.

Consider a metallic chassis upon which an electric circuit is constructed in some form or fashion. The chassis is used as the circuit 'common' (a term I much prefer over 'ground').

Good point! - Omegatron

Assume that the circuit is isolated from Earth ('ground') and is battery powered. Now, place charge on the metallic chassis. Because the chassis is conductive, the charge placed on the chassis distributes itself such that the electrical energy is minimized. The chassis is the zero volt reference point for the circuit. But, since the chassis has net charge, the chassis is at some potential w.r.t ground. Thus, we can define a capacitance for the circuit that is the total charge place on the chassis divided by the potential of the chassis (the Earth is considered to be our zero reference). Now, if a particular node in the circuit is 5V w.r.t. the chassis and the chassis is, say, 1000V w.r.t. the Earth, the node, by KVL, must be at a potential of 1005V w.r.t Earth, right? Perhaps we're saying the same thing differently so let's just leave it at that. Alfred Centauri 01:55, 30 May 2005 (UTC)

I was just saying that the chassis/common node is the only thing that gets that charge, at first. The charge "distributing itself such that the electrical energy is minimized" will take time to go through inductors, will never go through the dielectric of capacitors, etc. So sections of the circuit that were capacitively coupled would not become charged. That is all I'm saying. - Omegatron 02:30, May 30, 2005 (UTC)

I'm not sure about being able to store more charge either, but I think you can. Hence the term "condenser". I am learning about this on other sites as well.  :-)

I'm going to venture that the term condenser is due to the notion that a capacitor is, in effect, a way of separating charge versus a way to store charge. Think about it... Each plate of the capacitor has plenty of charge but there is an equal amount of positive and negative charge so there is no 'net' charge. When we move electrons from one plate to the other, we are more or less separating or organizing the charge that already exists in the plates into separate regions. Alfred Centauri 01:55, 30 May 2005 (UTC)

Yes, we are separating charge when we use a capacitor in a circuit. I wonder if the original (I've been reading some old patents lately) formulation of the capacitor was more general, and the term "condenser" came about because you could store more charge on one plate if it was near another plate that was connected to a charge reservoir than you could if the plate were floating by itself. And when I say "more charge" I am talking for the same voltage or same initial charged object or something. I am asking about this elsewhere as well... - Omegatron 02:30, May 30, 2005 (UTC)

When I say "discharge the cap", I mean discharge the cap by connecting its two terminals together. Say you have a cap floating through the air, lifted by invisible magical hands (or just held up by some piece of plastic). It has two terminals, A and B. If you scuff your feet along the floor and touch terminal A, the A side of the capacitor now has a net charge, while the B side is neutral. If you then connect a little lamp between A and B, the charge imbalance will settle out by sending a current through the lamp. Now both sides of the cap will have a static charge, but less so than side A was. - Omegatron 20:50, May 29, 2005 (UTC)

But, even though the charge is now distributed equally on the two plates, the capacitor has a net charge an thus a potential w.r.t. to Earth. Thus, by connecting both leads together on one side of a litte lamp with the other side of the lamp connected to Earth ('ground'), the charge you orginally placed on the terminal A can move from the capacitor through the lamp to ground, right? Somehow, this seems like double dipping. I've got to think about this a little longer... Alfred Centauri 01:55, 30 May 2005 (UTC)

Well, if you charge up any object and then connect it to another object that is differently-charged, a current will flow as the charge redistributes itself. In my example plate A is charged and plate B is neutral, so the charge redistributes itself when you connect them together, causing a current to flow, even though you didn't pull the charge off one plate and put it on the other. You just added extra to one plate from another object. Yes, the entire cap will always have net charge now unless you connect (both plates!) to something else. There is a certain amount of work involved in moving a certain amount of charge to plate A of the capacitor. If you do work redistributing that charge equally to plate A and plate B, does that reduce the work you can do in draining that charge back to ground? It seems like it would in order to conserve energy. So, something doesn't smell right to me so I'll have to get back with you on this one... Alfred Centauri

It takes work input to add charge to plate A. This creates a charge imbalance. You get work back out by letting A and B settle out, same as any other discharging of a cap. I am guessing half the work back out. Whoa I just thought of a way to try this with real capacitors.  :-) - Omegatron 03:19, May 30, 2005 (UTC)

OK, let's look at this another way. This problem is essentially the same as the 'missing energy paradox' when an uncharged capacitor is connected directly across an identical but charged capacitor. Plates A and B represent two identical conductors in free space (for simplicity here, assume the plates are in a vacuum). There is some capacitance C associated with each plate (this is the capacitance associated with this configuration of conductors and 'ground' and is NOT the same as the capacitance of the capacitor formed by the two conductors). Now, place Q amount of charge on plate A so that plate A has some voltage $V={\frac {Q}{C}}$ w.r.t. 'ground' . The energy stored in this configuration is ${\frac {Q^{2}}{2C}}$. Now, connect plate B to A via some resistance. Eventually, plate A and plate B will each have a net charge of Q/2. The total stored energy of this configuration works out to one-half the original configuration - half of the original electric energy was converted to thermal energy in the resistor as the charge redistributed. Alfred Centauri 14:25, 30 May 2005 (UTC)

Yeah I understand that all fine. - Omegatron 15:04, May 30, 2005 (UTC) Hmm... not what I expected. There's more to this than I think. - Omegatron 03:33, May 30, 2005 (UTC)

are you missing energy? Let the resistance mentioned above tend to zero and there seems to be paradox. If the resistance is zero, no electrical energy can be converted to thermal energy. So, where did the missing energy go? The answer is suprising! Alfred Centauri 14:25, 30 May 2005 (UTC)

No, different problem. I understand the resistance of wires just fine.

I know that you do. But that's not the source of the paradox. With near zero resistance, the flow of charge from one plate to the other occurs so quickly that we can no longer ignore the effects of EM radiation. Some of the electrostatic energy is converted to EM waves. Remember spark-gap radios?

Take four neutral conductive spheres, A, B, C, and D. Now connect a source between A and B. Some charge will move from A to B, and now A will have charge Q while B has charge -Q. Now touch A-->C and B-->D. A = Q/2, B = -Q/2, C = Q/2, D = -Q/2. Right? V_AB = V_CD and you should get an equal current when you discharge A to B and C to D.

Although there may be some configuration of spheres for which this is true, it is not true in general. When you charge the capacitor formed by spheres A and B, you do get Q on A and -Q on B. However, it is not necessarily the case that you get the Q/2 charge distribution when you connect A to C and B to D. Remember that the lowest energy configuration for equal and opposite charge concentrations is when the distance is minimized. The amount of charge that moves to sphere C depends entirely on where sphere C is w.r.t. spheres A and B! IMHO, this 4 sphere scenario introduces to much complexity. There is a simple setup that will answer your original question. Alfred Centauri 16:44, 30 May 2005 (UTC)

But now try the same thing with two identical capacitors, one with plates A and B, and the other with plates C and D. No (noticeable) charge is transferred and V_AB= the original source voltage, while V_CD=~0. If any charge is transferred, it is negligible compared to the charge imbalance on AB. I am clearly missing some fundamental capacitor concept. - Omegatron 15:04, May 30, 2005 (UTC)

I'm not sure if you should be thinking of the Earth as the universal reference point. The earth is just a big conductive sphere. It's not necessarily neutral. In my opinion, anyway. - Omegatron 02:30, May 30, 2005 (UTC)

What we are looking for is something that has, in effect, an infinite capacitance - a infinite 'sink' (or source) for charge. The Earth is, for all practical purposes, that object. Thus, it is our best zero reference point. Alfred Centauri 03:08, 30 May 2005 (UTC)

---

Here is a better description of my "condensed charge" question.

In case A, a metal sphere is charged up and brought in contact with another, neutral, identical sphere. The excess charge redistributes itself so that each sphere now has 1/2 the excess charge, right?

In B, the neutral sphere is now 1/2 the mass/volume/whichever is important here. This time only 1/3 of the charge is distributed to the smaller sphere, because there is "less room" for it to fit.

In C, the exact same thing as B, except the smaller sphere has been hammered out into a thin plate. The physical shape of the second object has no effect on how much charge will be transferred, does it?

Hmmm... The lowest energy configuration is for the individual charges to be infinitely far apart, right? Now, take the hammering of the smaller sphere into a thin plate to the limit - create an infinitely thin disk that is infinite in extent. My guess is that all of the charge from the first sphere moves onto the disk. What think? Alfred Centauri 03:34, 30 May 2005 (UTC)

Oh right! The shape does matter! Because they are trying to get as far away from each other as possible. Obviously the sheet can only be spread out to one atom thick, but most of the charge would be on that very wide disk, since it can be farther apart that way.

But what does this revelation do to the difference between C and D, if they have identical plates? - Omegatron 03:51, May 30, 2005 (UTC)

In D, the same exact plate as B, except now a thin insulating plate has been stuck to the metal plate, and another conductive plate placed very close. How much charge gets transferred to the plate now?? - Omegatron 03:14, May 30, 2005 (UTC)

Perhaps this will help. Consider a single metal plate isolated above an infinite conductive plane (a ground plane). The plate and ground plane form a capacitor. Connect the positive terminal of a 1V battery to the plate and the negative terminal to the ground plane. There will be charge Q deposited on the plate. Thus, the capacitance of the plate is Q farads. Now, remove the battery and discharge the plate to the ground plane. Stick the insulator to the plate and place a second, identical plate on the insulator. If we connect the positive terminal of the 1V battery to plate 1, will the amount of charge deposited by the same as before? If so, then the answer to part D of your problem is 'the same amount as in part C'. In effect, we are asking if the presence of the insulator and conductor changes the capacitance of the capacitor formed by plate 1 and the ground plane. It seems to me that the capacitance must change. The presence of the insulator and plate 2 change the electric field around the charged plate 1 which must change the capacitance. Further, it would seem likely that the orientation of the assembly w.r.t. to the ground plane will affect the capacitance. Thus, I think the answer to part D is that the amount of charge transferred is different from the amount transferred in part C. Alfred Centauri 16:44, 30 May 2005 (UTC)

Here is some added detail to my comment about orientation above. Assume plate 1 is initially above and parallel with the ground plane. If you place the insulator and plate2 beneath plate 1, you have inserted two additional dielectric layers between plate 1 and the ground plane (recall that a conductor has in infinitely large dielectric constant). This must act to increase the capacitance so more charge would be stored on plate 1 for the same potential. On the other hand, if the insulator and plate 2 are placed on top of plate 1, I don't see how the capacitance would be effected (ignoring fringing effects) so the amount of charge stored would be the same as without the insulator and plate 2.

Regarding the term 'condensor', I have a hunch that it might be based on the idea that the electric field is 'condensed' into the region between the plates instead of all space as in the case of an isolated object with a potential referenced to the zero at infinity. This has been a fun discussion. Thanks! Alfred Centauri 23:28, 30 May 2005 (UTC)

charge pump

So everyone knows that if you connect a voltage source to a capacitor, the voltage across the cap logarithmically ramps up until it reaches the voltage of the source, and then stops. What happens if you connect a current source? I guess this is equivalent to have an open-circuited ideal current source or a short-circuited ideal voltage source; an impossibility. (What's the difference between a charge pump and a current source?) - Omegatron 00:07, May 28, 2005 (UTC)

Right; you'd have to have an ideal current cource if you wanted to see the capacitor voltage go to infinity. But just like real-world voltage sources don't have a zero-ohms output impedance and can't deliver infinite current, real-world current sources don't have infinite impedance and can't deliver infinite voltage.

Charge pump usually refers to a circuit that places charge on one or more capacitors in parallel, then re-arranges the circuit to place the capacitors in series or reverses their polarity. It's sort of a "transformer for DC". They're used a lot in electronic circuits where you need a small amount of current at a higher-voltage and/or opposite polarity than the ordinary supply voltage. For example, the supply voltage may be +5 volts but the communications circuitry may need a couple of milliamps of +/- 12 volts. A charge pump can be used to produce this power. Charge pumps are related to voltage doublers/voltage multiplier and Cockroft-Walton voltage multipliers.

As you probably realize now, a current source is a different concept.

Atlant 00:18, 28 May 2005 (UTC)

Ok. I knew some of that. Somehow had the idea that charge pumps are the same as current sources, though. I've also seen "charge amplifiers" with capacitive negative feedback. So it seemed to me like voltage, current, and charge circuitry are different things. Maybe that charge is just another word for one of the others... - Omegatron

To be precise, an ideal voltage source is that two-terminal circuit element where the voltage across the element is independent of the current through it. Thus, if you connect an ideal voltage source across an ideal capacitor, the voltage across the capacitor instantaneously becomes the voltage across the voltage source which implies that the source supplied an impulse of current (an infinitely large and infinitely short 'pulse' of current). Obviously, there is no such thing as an ideal voltage source. All real voltage sources are modeled as an ideal voltage source in series with a resistor. So, when a real voltage source with open-circuit voltage V is connected to a capacitor, an RC circuit is formed so that the time for the capacitor to charge to about 0.99V is about $5RC$ seconds. The voltage across the capacitor is an inverse exponential:

$v(t)=V(1-e^{\frac {-t}{RC}})$

On the other hand, an ideal current source is that two-terminal circuit element where the current through the element is independent of the voltage across it. Thus, if you connect an ideal current source across an ideal capacitor, the current through the capacitor is constant so, by $i=C{\frac {dv}{dt}}$, the slope of the voltage across the capacitor is constant. That is, the voltage across the capacitor is a linear function of time which says that the voltage across the capacitor can become arbitrarily large. Once again, there is no such thing as an ideal current source. A real current source is modeled as an ideal current source in parallel with a resistor. So, when a real current source with short-circuit current I is connected to a capacitor, an RC circuit is formed just as is the case with a real voltage source. The voltage across the capacitor is given by:

$v(t)=IR(1-e^{\frac {-t}{RC}})$

Alfred Centauri 14:42, 28 May 2005 (UTC)

That's significant. Didn't know that. Apparently Van de Graaff generators are "current sources" though both sources can be made equivalent to each other through source conversion. What happens if you connect one to a cap? I guess source transformation is the key here. Both are really the same thing. - Omegatron 15:37, May 28, 2005 (UTC)

That's correct. Consider an ideal voltage source with a series resistance equal to (V / x) ohms where V is the source voltage. Let V tend to infinity and, in the limit, you get an ideal current source of x amps. That is, an ideal current source is, loosely speaking, equivalent to an 'infinite' voltage source in series with an 'infinite' resistance. The dual of this is an ideal current source with a parallel conductance equal to (I / x) siemens (or mhos) where I is the source current. Let I tend to infinity and, in the limit, you get an ideal voltage source of x volts. A Van de Graaff generator is a very high voltage source with a very high internal resistance so it can approximate a (weak) ideal current source. If you connected this to, for example, a 1uF capacitor, I imagine that the capacitor would charge rather slowly and quite linearly up to its dielectric breakdown voltage... Alfred Centauri 16:31, 28 May 2005 (UTC)

When you think about how a Van de Graaff generator works, it makes sense that it can be modeled pretty closely as an ideal current source connected to a capacitor. Think about it: We have the electrode at the base injecting a pretty-steady stream of electrons onto the belt. A steady stream of electrons is, of course, the exact definition of a constant current. These electrons are then transported on the belt from which they are dumped onto the metal sphere. The sphere accumulates the electrons and, in doing so, acts as one plate of a capacitor with the surroundings acting as the other plate and the air acting as the dielectric. Electron transport on the belt continues and the voltage on the sphere keeps rising until limited by electron transport off the sphere via corona, spark discharges, or leakage along the column and belt. Atlant 20:04, 28 May 2005 (UTC)

I've just taken a look at the article Van de Graaff generator and there are some problems. The first problem is related to this discussion. From the introductory paragraph:

"The generator can be thought of as a constant-current source connected in series with a very large electrical resistance."

This is just silly. Connect a 1A constant-current source across a resistor of R ohms. The voltage across the resistor is R volts, right? Now, put a 'very large electrical resistance' between the constant-current source and the resistor. The voltage across the resistor doesn't change - it is still R volts. Alfred Centauri 18:25, 29 May 2005 (UTC)

You're right. I changed series to parallel. --Heron 20:04, 29 May 2005 (UTC)

Re-factor to "Electrolytic capacitor"?

DavidCary asks: "Should I move all but a brief summary (of the Electrolytic capacitor section) to Electrolytic capacitor ?"

I'm not a big fan of re-factoring into a lot of smallish articles, but I suspect there's enough meat here to make a reasonable sub-article. So I guess it's okay by me. Let's see what some others think as well...

Atlant 23:58, 1 Jun 2005 (UTC)

I agree. - Omegatron 01:53, Jun 2, 2005 (UTC)

Assuming this gets consensus approval, please be sure to re-write the Electrolytic capacitor so that it includes more than just ordinary aluminum electrolytics; right now it's written as if they were the only electrolytic caps in the world; our own summary here provides better coverage of the varieties.

Atlant 11:36, 2 Jun 2005 (UTC)

Applications

A friend and I are both guitarists and we've been having a discussion about the tone controls on a guitar. It turns out that a bass tone control is just a high-pass filter made of a capacitor and a pot in series while a treble tone control is a low-pass filter with a pot and capacitor in parallel. We understand the what, but don't understand the how. How/why does the capacitor have this effect on a signal? Maybe I'm missing the information in the article, but I don't see how the capacitor has this function. Might be a good addition to the applications or some other section. - MordredKLB 21:40, July 14, 2005 (UTC)

First, you should probably be looking at lowpass filter and highpass filter. A simplistic way to think of it is that a resistor resists all frequencies the same, but a capacitor has more resistance at low frequencies than high. (The lowest frequency; 0 Hz, or DC, can't pass through a capacitor at all.) But why does that happen, you ask? Hmmm... - Omegatron 02:00, July 15, 2005 (UTC)

I understand that and the low/high pass articles were where I got my information originally. Okay if a capacitor has more resistence at low frequencies then why does altering the resistence in series with the capacitor vary the amplitude of the low frequency? When the bass knob (pot) on my guitar is at ten, why does the capacitor have no effect (yes there is some effect just from being in the circuit, but it's minor) on the tone? - MordredKLB 15:51, July 15, 2005 (UTC)

Because it's a voltage divider. The output voltage is the input voltage times the ratio of the two resistances. So if the capacitor is a smaller resistance for high frequencies, the output voltage will be different at those frequencies.

Can you describe your guitar circuit in more detail? Does it look like the images in the filter articles? - Omegatron 16:15, July 15, 2005 (UTC)

Yes the wiring diagrams do look like the images in the filter articles. For the treble control I've got a standard 3-prong pot. The input of the pot is coming from the input of the volume pot. The capacitor is hooked up to variable prong on the pot and the other end is connected to ground. I'm wishing I had paid more attention in my E&M class. Maybe I should just stop worrying about why it works and be content that it does. - MordredKLB 17:21, July 15, 2005 (UTC)

Article or Application para Splitting?

What is this stuff about -- anybody know??? I think the Application section of this article is rather messy, somethings seems to be repeated and others not that great explained. I made some editing and proposed this (below) as a replacement, where the applications has been catergorised. However, I am not a native english speaker and I am no authourity on the subject so I posted it here so someone with more knowledge can approve, correct, alter or dissaprove.

The application is great for not so into it users. But I think it is rather messy right now. I think the following suggestion (after language corrections and other) makes things more clear, obs this will probably mostly be a section for newcomers.

Applications Capacitors are found in almost all electronic devices. They are mostly used to give an even power supply, for filtering electric signals and for storing charge.

Storing charge:

A capacitor can store electric energy when disconnected from its charging circuit, so it can be used like a temporary battery.

The energy stored in a capacitor can be used to represent information, either in binary form, as in computers, or in analogue form, as in switched-capacitor circuits and bucket-brigade delay lines. (Isn’t this usally done by transistors?)

Filter frequencies:

As a capacitor will resist low frequencies it is used to design electric frequency filters. High pass filters are often used to separate the AC and DC components of a signal. This method is known as AC coupling. Lowpass filters which filters signals with high frequencies can also be designed.

For example, radio receivers rely on variable capacitors to tune the station frequency. Speakers use passive analog crossovers, and analog equalizers use capacitors to select different audio bands.

Capacitors can be used in analog circuits as components of integrators or more complex filters and in negative feedback loop stabilization. Signal processing circuits also use capacitors to integrate a current signal.

Smoothing power supply:

In applications where very rapid or very large current surges may occure or where the power supply has to be very stable capacitors are connected in parallel with the power circuit. For example, in logic circuits a set of capacitors with descending capacitances is used to evenly supply the rapidly changing current surge. The smallest capacitors feed the circuit at a higher speed than is possible from the bigger capacitors or the direct power supply. After discharging the smaller capacitors are rapidly charged by slightly bigger capacitors and ready to be discharged in the next cycle. The capacitors act as a local reserve for the DC power source, and bypass AC currents from the power supply.

For larger systems (such as factories) they are used to shunt away and conceal current fluctuations from the primary power source to provide a "clean" power supply for signal or control circuits.

Capacitors are used in power factor correction. Such capacitors often come as three capacitors connected as a three phase load. Usually, the values of these capacitors are given not in farads but rather as a reactive power in Volt-Amperes reactive (VAr). The purpose is to match the inductive loading of machinery which contains motors, to make the load appear to be mostly resistive. (I don’t really get this section)

Sensors: Capacitors with an exposed and porous dielectric can be used to measure humidity in air. Capacitors with a flexible plate can be used to measure strain or pressure.

Don’t know how to classify: Capacitors are also used in parallel to interrupting units of a high-voltage circuit breaker in order to distribute the voltage between these units. In this case they are called grading capacitors. Capacitors are used as the transducer in condenser microphones.

An obscure but illustrative military application of the capacitor is in an EMP weapon. A plastic explosive is used for the dielectric.

Move section and picture to other place in Capacitor In schematic diagrams, a capacitor used primarily for DC charge storage is often drawn vertically in circuit diagrams with the lower, more negative, plate drawn as an arc. The straight plate indicates the positive terminal of the device, if it is polarized (see electrolytic capacitor). Non-polarized electrolytic capacitors used for signal filtering are typically drawn with two curved plates. Other non-polarized capacitors are drawn with two straight plates.

Move to EMP The capacitor is charged up and the explosive is detonated. The capacitance becomes smaller, but the charge on the plates stays the same. This creates a high-energy electromagnetic shock wave capable of destroying unprotected electronics for miles around. These devices were first employed by the US in the 2003 invasion of Iraq.

Capacitor- Capacitance Distinction

I agree with Ian Cairns (Dec 2004) that capacitance and capictors should be treated as separate but linked articles. A capacitor is a manufactured component-- capacitance is a physical phenomenon. Does anyone want to do the split?? Al I removed the capacitor networks bit from capacitance anp ut it in to capacitor wher Ithought most people had agreed it should go. But my deletion was reverted by Func who said it was 'blanking'. Can anyone tell me how to legitimately move material from one article to another?? Thanks Light current 05:33, 1 August 2005 (UTC)

It's quite common for vandals to just arbitrarily delete text from articles, so if a bunch of text disappears without coment, many folks will automatically revert it back in.

To avoid this, just make sure you add an appropriate "comment" to the audit trail in the article from which you deleted the text. And if you can't explain your change using an audit-trail "one-liner", use the audit trail comment to refer people to the article's talk page and explain yourself there.

(And if you did explain yourself, then I have no explanation for why you were reverted.)

Atlant 11:47, 1 August 2005 (UTC)

Size of Page

The capacitor article is now reaching its upper size limit. Any suggestions on how to split it??Light current 00:52, 2 August 2005 (UTC)

The limit is arbitrary, and imposed solely for the benefit of ancient browsers that didn't want to edit "text" input fields of greater than 32KB size. Ignore it until the article gets a lot bigger.

Atlant 12:07, 2 August 2005 (UTC)

electrosplitic

Yes, split all of the electrolytic capacitor section except a summary into its own article. - Omegatron 23:26, August 18, 2005 (UTC)

Huh?

C0G and NP0 (negative-positive-zero, i.e. ±0) dielectrics have the lowest losses

What does that mean? - Omegatron 23:26, August 18, 2005 (UTC)

I dont think the statement is necessarily true. It may be true that some C0G/NP0 have low loss but I think for instace an air spaced cap or a vacuum cap woul show even lower loss! Light current 23:42, 18 August 2005 (UTC)

Omegatron, which part of that didn't you understand? (And I'm not being snippy or sarcastic; I'm seriously asking.)

Atlant 23:53, 18 August 2005 (UTC)

Arent all capacitors really only transmission lines?

discussion moved to Talk:transmission line by LC 17/10/05

'Displacement' current in transmission line?

moved to talk:transmission line by LC 17 oct 05

"Transmission line" fed at both ends

moved to talk:transmission line

===Light current message for you at=== [2] also see discussion at [3] Scott 00:45:01, 2005-09-12 (UTC)

Capacitor type vs. frequency

Has anyone thought about adding a graph of the different capacitor types vs usable frequency ranges?

No I know this might raise some eyebrows, but I believe that most types are OK at very high frequencies as long as the leads are very short (assuming a reasonable dielectric)--Light current 02:43, 14 September 2005 (UTC)

Condenser

My father was an amateur radio operator (Ham) who studied electronics at a radio college in Toronto, Ontario in the mid-1930s. He built his own transmitters, and did radio repair for many years. He always used the term "condenser". I remember that well from my childhood in the 1960s: he never ever referred to condensers as capacitors even into the 70s or 80s. When did the name change to capacitor "officially" happen? —Preceding unsigned comment added by 68.71.8.39 (talk) 12:41, 6 January 2011 (UTC)

Who coined the term "battery" ?

Multiple references attribute the first usage of the term "battery", when applied to a group of Leyden jars, to Benjamin Franklin. Some references attribute it to Daniel Gralath. We have a letter from Franklin himself, dated 1748, in which he states, "Upon this we made what we called an electrical-battery".(ref, page 28) I haven't found any reference illustrating Daniel Gralath using this term at a date which precedes Franklin's letter. If no such reference exists, I would give Franklin the benefit of the doubt for having coined the term. A recent edit to the article changed the wording from created to adopted, and I question the historical validity of this change. Wildbear (talk) 06:04, 9 July 2010 (UTC)

I agree. Maybe I'm biased toward my own text, but I don't think that copyedit improved much. It now also suggests that using plates is somehow obsolete. Support undoing it. Potatoswatter (talk) 06:21, 9 July 2010 (UTC)

Picture

Why does the picture have a direction for V? — Preceding unsigned comment added by Schilippe (talk • contribs) 04:47, 30 March 2011 (UTC)

Electrolytic capacitor explosions

The article currently states that high-voltage electrolytic capacitors can explode if exposed to voltage beyond their rated limit. It does not have to be just high-voltage capacitors. When I was in high school, some one apply 20V across a capacitor rated for only 16V. It went bang spectacularly.

I am going to remove the "High-voltage" part from this line.

Nutster (talk) 05:46, 22 March 2011 (UTC)

I think the point was that high-voltage capacitors pose a particular safety issue. In a low-power electronic application, sure, it is possible for capacitors to explode but it is not a serious matter when it happens and it does not happen often because capacitor voltage ratings are often many times the working voltage (the exception is tantalum capacitors which have comparatively low voltage ratings and when they go make a repulsive smell to boot). On the other hand workers testing high-voltage power supplies can be required wear safety goggles to protect their eyes in the event of a reservoir capacitor explosion. Explosion of compensating capacitor banks on the power grid would be more than a high school prank, it would be a serious incident. SpinningSpark 09:04, 30 March 2011 (UTC)

White material around base of capacitor

What is the likely purpose of a hard white material placed around the base of one lead of a capacitor? This is on several but not all capacitors on a board.

I'm guessing it is either to reduce vibration or to increase resistance. I would appreciate knowing what it is for.

Thanks, Wanderer57 (talk) 00:25, 31 March 2011 (UTC)

Hard to tell from the description. It might be a spacer, used to ensure consistent clearance under the part for board washing. But I'm speculating. --Wtshymanski (talk) 02:21, 31 March 2011 (UTC)

It sounds like adhesive staking material.--Asher196 (talk) 02:31, 31 March 2011 (UTC)

AC use

There is no explanation how series use of capacitors adapts them to AC. —Preceding unsigned comment added by 82.193.151.2 (talk) 13:15, 23 May 2011 (UTC)

Why there is a phase shift between current and voltage in a capacitor

(an intuitive explanation by using hydraulic analogy)

IMO it would be interesting to see the correspondence below between me and a curious web reader about the phase shift phenomenon in capacitors driven by AC. Circuit dreamer (talk, contribs, email) 09:14, 26 June 2011 (UTC)

QUESTION: Im having a really hard time trying to understand what the phase shifts mean in real life in a circuit (I know it means current lags source voltage by X amount..but how). I understand them mathematically but not in physicality, mainly because I cant find any explanation.

ANSWER: Let's explain for now the 90 deg phase shift between current and voltage in a capacitor. I recommend to you to think "hydraulically" ("electrical current - water flow" and "voltage - water level") to understand intuitively the phase shift idea.

Well, imagine you fill (sinusoidally) a vessel with water and you picture graphically this process. Choose the half of the maximum water height as a zero level (ground). So, you first open and then close (sinusoidally) the supply faucet. But note no matter you close the faucet (in the second part of the process) the level of the water will continue rising; it is strange that you close the faucet but the water continue rising. Finally, you have completely closed the faucet (zero current), but the level of the water will be maximum (maximum voltage).

Now, at this point, you have to change the flow (current) direction to make the water level decrease. For this purpose, you open and then close another faucet at the bottom to draw the water (now you draw current from the capacitor). But again, no matter you close the faucet the level of water will continue falling; it is strange again that you close the faucet but the water continue falling. Finally, you have completely closed the faucet (zero current), but the level of the water will be maximum negative (maximum negative voltage).

So, the basic idea behind all kind of such storing elements (named integrators) is:

The sign of the output pressure-like quantity (voltage, water level, air pressure, etc.) can be changed only by changing the direction of the input flow-like quantity (current, water flow, air flow, etc.); it cannot be changed by changing the magnitude of the flow-like quantity. At this point, the current is zero but the voltage is maximum; this gives the 90 phase shift on the graph.

Circuit dreamer (talk, contribs, email) 09:14, 26 June 2011 (UTC)

More History

Construction:

• insulating plates and foils interleaved
• insulating sheets and foils wound, with conncetions to foils at one end (standard 1920s type)
• connctions to foils all over, achieved by displacing the foils slightly sideways and using side connections pressed against them (used in 1930s)
• plastic dielectrics that weren't severely lossy at rf
• metallisation of the dielectric replaces foils - better capacity per volume, accuracy and stability
• ceramic dielectrics

Electrolytics:

• Wet, must be used upright
• not sure what to call them, but not the above
• Acid etched plates

I don't know the dates of all these though. Tabby (talk) 05:53, 10 July 2011 (UTC)

Electrolytics in Series for AC

Addressing the "This paragraph needs attention from an expert..." banner under Series Capacitors, I don't believe the statement "Series connection is also used to adapt electrolytic capacitors for AC use. 2 polarised electrolytics are connected back to back. Such arrangements have their issues." is true at all. I've never seen or heard of it in practice and common electronic sense would say that this would reverse one of the capacitors every half-cycle resulting in the eventual destruction of both. Sleepsfortheweak (talk) 23:48, 4 October 2011 (UTC)

It's called a "bipoloar capacitor" and is very commonly used in such things as speaker crossover networks. It's at least mentioned at Electrolytic_capacitor#Types though it needs a reference. Back in my hobby electronics days, when the parts were big enough to see, you were often advised in magazine project articles to put two regular electrolytics back-to-back if you didn't happen to have a bipolar capacitor handy. --Wtshymanski (talk) 15:26, 5 October 2011 (UTC)

Thanks for the input. I've seen Bipolar Electrolytics before but didn't realize internally they were effectively two polarized caps in opposing series. I've found several mentions of doing this but also several people mentioning the need for shunt diodes to 'short' the reversed cap during each phase. This makes more sense to me, but apparently people have been ignoring diodes successfully too, so I'm currently looking for a credible source or maybe just trying both myself. Sleepsfortheweak (talk) 02:59, 6 October 2011 (UTC)

Real bipolar electrolytics actually have only two electrodes just like unipolar, but each electrode has teh full strength oxide dielectric layer; it's a little more space-efficient than two pairs of plates. It's probably application dependant; it looks like a regular unipolar electrolytic can only tolerate a small reverse voltage, perhaps in some applications there's not enough leakage to cause excess voltage across the reversed capacitor without a diode. I meant to look this up in Horowitz and Hill, but haven't had a chance yet. --Wtshymanski (talk) 14:03, 6 October 2011 (UTC)

(days later) Horowitz and Hill had nothing useful to say on bipolar capacitors...they really don't like electrolytic capacitors of any sort, do they? --Wtshymanski (talk) 20:57, 10 October 2011 (UTC)

How about somebody find a credible source that discusses reliable use of electrolytics in series for AC applications, or else delete the offending paragraph altogether?--173.69.135.105 (talk) 23:59, 26 October 2011 (UTC)

I prefer that we find credible sources to cite and keep the application info. As an electronic design engineer of some ten years I can say from experience that sometimes the non-polar electrolytics in the size/value/price that you want are not available. This forces one to use the 'back to back' polar elcap arrangement described. It must always include the shunt diodes to protect each polar elcap from reverse potential for reliability and _safety_. I will trawl some capacitor manufacturer info later to try to find cit-able source.Regards, Soldersplash (talk) 12:37, 14 November 2011 (UTC)

I always thought that the shunt diodes were needed. The conceptual model that one diode is on during each half cycle, shorting out the corresponding cap isn't quite right. What really happens is that the node between the two caps gets charged up (or down, depending on whether the + or - ends are connected together) and stays charged, so that both caps are biased with sufficient dc that their voltage never goes negative. The reliable source we have cited there (app note from a cap manufacturer) says that you don't really need the diodes, because the caps will act as diodes and conduct in the reverse direction to accomplish that effect. I would think it would be more reliable to have that reversed current flow through a diode, but given that it's only a transient phenomenon as the cap charges up I can see that in some applications it could be acceptable to do it without the diodes. Ccrrccrr (talk) 14:56, 19 November 2011 (UTC)

I haven't found anything that discusses this in sufficient detail - somewhere there's an application guide that gives the limits of the shunt diode method. I've never heard of back-to-back unipolar electrolytics being used for motor starting capacitors, for example, shunt diodes or not. It may only be a feasible technique at low power and low frequency. --Wtshymanski (talk) 17:32, 20 November 2011 (UTC)

I think of it more as a hobbyist/prototyping method for making something work with what you've got around the lab/garage, than as something one would want in a production design. In addition to applications which involve low-frequency AC applied across the cap, it can be useful for situations in which the voltage is primarily dc, but the dc value might be positive or negative at different times. Ccrrccrr (talk) 21:35, 20 November 2011 (UTC)

Shocking Quotes Incorrect

It says in the article that Ewald Georg von Kleist of Pomerania said "I would not take a second shock for the kingdom of France." Following the citation to the primary source reveals that this is a quote from the Dutch physicist Pieter van Musschenbroek, taken from a letter to Reaumer(?). Musschenbroek also says in the letter, "I felt myself struck in my arms shoulders and breast. I lost my breath, and it was two days before I recovered from the effects of the blow and the terror." Von Kleist does write (of the Leyden Jar) "If while it is electrified I put my finger or a piece of gold which I hold in my hand to the nail I receive a shock which stuns my arms and shoulders" The quotation attribution should be changed in the article. Jake Papp (talk) 17:16, 9 September 2011 (UTC)

Capacitors in Series for HV

It's bad practice to use capacitors in series for HV in cases where a single capacitor is not rated for the full voltage.

Ideally, the voltage difference across each capacitor would be the same and this would be an effective technique; however in practice each capacitor has (potentially very) different leakage current leading to inequal voltage division. This can lead to one capacitor becoming overloaded and breaking down, causing a chain reaction and total failure of all the capacitors. It's much, much safer to use a single capacitor rated for the full voltage. — Preceding unsigned comment added by 64.106.63.246 (talk) 23:09, 13 December 2011 (UTC)

Capacitors for storing charge or not

Re the recent discussion in edit notes: "Capacitors don't store charge - a given capacitor has the same total charge when 'charged' as when 'uncharged'."

It's more correct to say that capacitors store current. It's even more correct, and more intuitive, to say that capacitors store electrical energy. — Preceding unsigned comment added by 64.106.63.246 (talk) 23:05, 13 December 2011 (UTC)

Probably I should explain that I'm writing this to clarify my thinking, NOT as an expert on capacitors.

When a capacitor is charged, one side has an excess of electrons and the other a comparative "shortage".

It may be true that the total charge (number of electrons) in the component is the same when charged as when uncharged, though I'm inclined to doubt that statement.

Even if it is true, it glosses over the point that excess positive charge is stored on one side (and excess negative on the other.)

Wanderer57 (talk) 21:48, 4 April 2011 (UTC)

I would be more willing to follow what authoritiative sources say, instead of what a random anon address thinks. --Wtshymanski (talk) 22:00, 4 April 2011 (UTC)

I agree. A capacitor stores charge: one plate stores positive charge and the other stores negative charge. Even if the phrase doesn't tell the whole story, its as good a capsule description as we're going to get, which is why it is used widely as a definition in "authoritative sources": 1, 2 3 4 5 Excessively complicated, esoteric introductory sentences are one reason people complain Wikipedia articles can only be understood by the people who wrote them. --Chetvorno^TALK 01:27, 5 April 2011 (UTC)

To reiterate: a capacitor stores charge, but then so does a wire, a brick, a human-being...anything containing charged particles. A capacitor is not for storing charge; a capacitor is for storing a certain configuration of charge - a charge separation. Compare this to a steel spring, which likewise stores steel (in that it contains steel), but is for storing steel in a specific configuration (compressed or stretched). 86.148.115.162 (talk) 05:43, 5 April 2011 (UTC)

Are you really helping explain capacitors here? --Wtshymanski (talk) 14:07, 5 April 2011 (UTC)

Hi 86.148... . . . It seems to me the PURPOSE of a capacitor is to store a charge. This is in contrast to a wire, a brick, a spring, or a boll weevil. There is more to the story of a capacitor than "it stores electric charge" but using the first sentence of the first paragraph of the article to delve into detail is not a good idea.

Also, re your sentence "a capacitor is for storing a certain configuration of charge - a charge separation.", aren't there applications in which the purpose of having a capacitor in the system is building up a stored charge on ONE side? Wanderer57 (talk) 16:02, 5 April 2011 (UTC)

Hi , Wanderer57. :) It's the 'more to the story' that gives a capacitor it's purpose - if to (merely) store charge were its purpose, then it could be substituted for a wire, a brick, a boll weevil (lol), etc. Shouldn't an introductory description of something mention the salient purpose of said something?

If by 'a stored charge on ONE side' you mean 'a stored charge on ONLY one side', that IS a certain configuration of charge - implicit in its definition is 'the other side, which has a different charge'. 109.158.70.33 (talk) 17:04, 5 April 2011 (UTC)

Thanks for the feedback. The point that got me into this discussion was whether it was appropriate for the OPENING SENTENCE of the article to basically say that a capacitor is a device for storing electric charge. I think it is. For a reader who is uninformed about capacitors, it gives a general idea of the kind of thing the article is about. For a reader wanting more depth, all they need do is to read on. The beginning of a technical article is supposed to be a "gentle" introduction to the subject, before getting into detail.

The whole bit about any material object storing charge is entertaining but sort of pointless. A capacitor is designed to allow charge to be stored and released in a controllable way. This is not true of the other objects mentioned. (Getting a real charge out of a boll weevil is nearly impossible, except maybe for entomologists.) Wanderer57 (talk) 19:29, 5 April 2011 (UTC)

No problem. How about changing the opening sentence to read 'a capacitor is a device for allowing charge to be stored and released in a controllable way'? 109.158.70.33 (talk) 20:37, 5 April 2011 (UTC)

Seems okay to me. Other comments? Wanderer57 (talk) 21:04, 5 April 2011 (UTC)

Although tolerable, I think this would raise more questions for nontechnical readers than it would answer. I like the original version; concise and understandable. --Chetvorno^TALK 21:16, 5 April 2011 (UTC)

I agree. The opening sentence should be correct but not overly precise. The rest of the section should form the rest of the summary of the whole article, and somewhere in the later sections the more esoteric details and more precise definitions can be covered. -- Nczempin (talk) 21:06, 8 April 2011 (UTC)

Fair enough. The current introductory sentence looks good - it concisely states that a capacitor stores energy in an electric field (just like an inductor stores energy in a magnetic field; to say a capacitor stores charge is like saying an inductor stores magnetic monopoles). -- 86.144.159.120 (talk) 21:52, 25 August 2011 (UTC)

I've always thought of it this way: A capacitor is a device that has capacitance. Capacitance is the ability to store energy in the form of an electrical charge. I don't think adding in something about a capacitor discharging is relevant in the opening statement because some capacitors are used, for example, to filter out direct current, and although they discharge it is not the primary function. Primium mobile (talk) 01:08, 4 June 2011 (UTC)

What is the capacitance of an isolated 1 meter square sheet of aluminium foil. It must have some intrinsic capacitance or adding a single electron would cause an extreme potential difference with it's surroundings! Anyway it is known from shell within shell calculations that conductive objects always have some intrinsic capacitance, I just can't find any information for the calculations for metal sheets. — Preceding unsigned comment added by 123.16.100.93 (talk) 01:25, 11 July 2011 (UTC)

--86.144.159.120 (talk) 21:52, 25 August 2011 (UTC)

Fallacy

Dielectric:

• It is a common mistake to invoke atoms, electrons, etc. in the dielectric region of a capacitor to explain its operation. This is a patently false explanation.
• The fact that a capacitor works in a vacuum puts the lie to that explanation. The simple fact is that a capacitor works via a vacuum-crossing, longitudinal electric field spanning the separation between the plates.

• Incidentally, the fact that a spherical-plate capacitors works is proof that the capacitor effect cannot be attributed to magnetic action either.
• The reason (in my opinion) that this fallacy is invoked to explain capacitor function is that the commonly applied simplifications of Maxwell's theory do not readily admit the existence of such a longitudinal effect. This causes college professors to look like jackasses when they try to explain it. They don't much like that.

• Given the above, what is the velocity of propagation of the longitudinal electric field across the separation between the plates (assuming a vacuum "dielectric")?
• For example, as the charge on one of the plates is varied, what is the velocity of propagation of that change to the opposite plate? — Preceding unsigned comment added by 134.223.116.200 (talk) 20:24, 21 November 2011 (UTC)

The electrostatic simplification of Maxwell's equations has an electric field between the charges on the plates. The properties of the material matter when it's not a vacuum, since polarizable materials have higher permittivity than free space. If there are professors who have trouble explaining, that's hardly relevant here. Making wild claims of "patently false" and "look like jackasses" don't make one look so good, either. And electromagnetic effects propagate through vacuum at the speed of light, though the dynamics of capacitor charging are typically slower, limited by propagation along the wires more than between the plates. And it's generally not OK to edit or remove the talk-page comments of others, as you did; but we'll let that slide. Dicklyon (talk) 23:08, 21 November 2011 (UTC)

Then you admit the propagation of a longitudinal electric (or similar?) field force in a vacuum at a finite speed? Without the presence of a magnetic component of any kind? A plasma wave, then, without any plasma? Thanks for clarifying. Also, thanks for letting it slide.

As for the speed of light, that presents some difficulty it seems to me. If a transverse wave with a perpendicular magnetic component propagates at the speed of light then a longitudinal pressure wave with no magnetic component must propagate... (I'm drawing a blank here.)

Another interesting thing I found while researching this on wikipedia. Surface wave Check out paragraph titled "Energy flow velocity". Interesting stuff, but clearly in error. Somebody should correct that one. — Preceding unsigned comment added by 72.95.47.115 (talk) 00:31, 22 November 2011 (UTC)

I think you confuse fields and waves. Fields don't propagate. Waves do. The electrostatic simplification is based on the assumption that there are no changes, i.e. nothing to propagate. As soon as you try to change the electric field by moving charges around, they start generating magnetic fields, and that's when the usual electromagnetic waves come into play. — Preceding unsigned comment added by 77.9.26.238 (talk) 19:46, 14 April 2012 (UTC)

Noise Filters and snubbers

Looking at this line: "When an inductive circuit is opened, the current through the inductance collapses quickly, creating a large voltage across the open circuit of the switch or relay."

Would it be more accurate/true to say the "magnetic field collapses"? — Preceding unsigned comment added by 120.148.70.96 (talk) 08:02, 28 February 2012 (UTC)

120.148.70.96 (talk) 05:46, 19 March 2012 (UTC)

DC circuits plot

I can't believe that an article on wikipedia about such a basic concept... the article must have been around for over a decade now... ... doesn't show a simple graph for the DC circuit. And instead bombards us with math. This is a recurring wikipedia as well as electronics-textbook/course theme that is hardly necessary to understand the basic idea. Kindergardeners could understand an RC circuit if it weren't for the math... which, by the way, didn't exist until *after* the circuits were experimented with in an attempt to explain what was already seen experimentally. If your audience is to those who have a very clear understanding of the term "exponential function"--so clear that they can intuitively visualize it in their minds with appropriate axes-labels and markings for what Tau=RC corresponds to, etc.--then the mathematial derivations are completely unnecessary, as this same audience can do those in their heads as well, and basically needn't be looking at a wikipedia article in the first place. Is this some sort of universal joke in the electronics field? It must be. — Preceding unsigned comment added by 71.197.246.206 (talk) 01:15, 20 October 2012 (UTC)

Electroluminescent (EL) wire

EL wire is a type of capacitor used in an AC circuit. The membrane is made of a phosphorescent material and the magnetic field activates the material. Should this be under capacitor, or is the article only for storage-discharge type capacitors? 76.21.107.221 (talk) 11:43, 29 September 2012 (UTC)

I know that all wire produce some capacitance and inductance, but I'm not familiar with EL wire. Do you have any sources which explain how they are used as capacitors? Zaereth (talk) 22:52, 29 September 2012 (UTC)

Back to back electrolytics

The paragraph on back to back electrolytic capacitors does not seem to match what I have always understood about them. Namely, the part about premature wear due to the reverse voltage that the capacitor experiences seems wrong. I have not been able to locate this information in the cited sources, but I have checked a few sources of my own. Nonpolar capacitors like this are used frequently as motor-start capacitors or in amplifiers. These capacitors experience no reverse voltage, because the negative side is isolated from the system. During one half cycle, one capacitor has positive voltage at the positive terminal, and the other has ground at the positive terminal. Durning the next half cycle, the other capacitor gets positive voltage at the positive terminal. They never see reverse voltage, because the negative terminals never see positive voltage. However, with this type of arrangement, the capacitance is cut-down by half and the capacitor's service ratings must be decreased by a factor of four, to compenstae for the increase in defects. Zaereth (talk) 20:57, 26 March 2012 (UTC)

It does'nt matter what happened in the electronics. Important is the internal construction of the capacitor. In bipolar aluminum electrolytic capactors with non solid electrolyte two anode foils are wound back to back to one winding, separated with a paper as protection against matallic contact and reservoir for the electrolyte. So if you put one 100 V foil forward and one 100 V foil backwart together, the capacitor can withstand from each side 100 V. --Elcap (talk) 02:10, 1 April 2012 (UTC)

I don't see any benefit in including the current paragraph on back to back electrolytic capacitors, I recommend that someone either deletes it, or adds information. If it is deleted, there are a number of statements that can be made instead, which amount to the same thing: 1. Polarised capacitors must be used in the correct polarisation to maintain working life. 2. Non-polarised electrolytic capacitors may be used to in the place of polarised electrolytic capacitors to prevent reverse bias (or maintain the correct polarisation). 3. Two equal value capacitors may be connected in series to achieve a halving of capacitance. 195.59.43.240 (talk) 10:18, 12 October 2012 (UTC)

DC circuits equation

I question whether the variables are correct in the "DC circuits" section. It has the first equation in there as V0 = i(t)R + 1/C int(i(tau)d(tau)). I think the two instances of tau should really be t to concur with the bounds of the integral. Ereisch (talk) 20:33, 30 March 2012 (UTC) - t in that equation is a value, not a continuous variable. You integrate over continuous variables, so the equation is technically correct. Personally, I'd swap all the t's and tau's, as tau tends to be used to represent values in units of time, while t is normally used to represent the continuous variable of time. 195.59.43.240 (talk) 09:58, 12 October 2012 (UTC)

I just caught this while reading the article as well, and checked here to see if anyone had seen it too. Use of a dummy variable is unnecessary in this case, and especially because the dummy variable symbol is already an important symbol for a constant, tau, used in many RC circuit equations, and so it is unnecessarily misleading and confusing. I agree that swapping tau and t would be the more conventional and practical way to show the equation, or even eliminate tau all together. --Electricfog (talk) 15:40, 26 December 2012 (UTC)

Wakefield experiment

The experimental results of "The Wakefield Experiment", http://www.ivorcatt.co.uk/x343.pdf , published in April 2013, contradicts the statement "a static electric field develops across the dielectric," in the article. When I added a hyperlink to "The Wakefield Experiment", it was promptly removed. Ivor Catt 13 April 2013 — Preceding unsigned comment added by Ivor Catt (talk • contribs) 09:14, 13 April 2013 (UTC)

Add Voltage Coefficient to Non-Ideal Behavior section

How about adding a paragraph about capacitor value on applied DC voltage in some types of capacitors (especially high-k dielectric ceramics)? This is a common problem which trips up analog designs found with timing circuits, etc. I can get this started from a parameter perspective but do not understand the physics. AnalogGround (talk) 18:38, 18 November 2013 (UTC)

Request for Discussion of {{Semiconductor packages}} in electronic articles

Please see the corresponding discussion thread at Wikipedia talk:WikiProject Electronics. Thanks! • Sbmeirow • Talk • 23:34, 15 December 2013 (UTC)

Semi-protected edit request on 31 March 2014

Reference 26 link is wrong. Please replace: http://www.johansondielectrics.com/technical-notes.html/age with: www.johansondielectrics.com/technical-notes/general/ceramic-capacitor-aging-made-simple.html Thanks. Robiki (talk) 10:23, 31 March 2014 (UTC)

 Done Indrek (talk) 11:54, 31 March 2014 (UTC)

Semi-protected edit request on 27 April 2014

Spelling error. Capacitors are commonly used in electronic devices to maintain power supply while batteries are being changed. Should be: Capacitors are commonly used in electronic devices to maintain power supply while batteries are being charged. Thanks! 69.133.32.134 (talk) 13:07, 27 April 2014 (UTC)

‘changed’ is a correctly spelt word, and I think it makes more sense here. Consider a device that can stay on briefly while its battery is swapped with another. This also applies to non-rechargeable batteries. —James Haigh (talk) 2014-04-27T13:48:29Z

"Replaced" would be more precise and less suspect. After all, charging a battery changes it. Macdust (talk) 20:48, 19 July 2014 (UTC)

Macdust (talk) 00:21, 13 June 2014 (UTC)== please remove hyperlinked reference to "displacement current" ==

The corresponding article shows fundamental disputation and obscurantism and there is no purpose to sending readers there. If you substitute the term "some current" for "displacement current", it is possible for the reader to continue learning about the topic of capacitors without having to escape a rabbit hole first. Macdust (talk) 21:50, 12 June 2014 (UTC)

If you feel there is a problem with the Displacement current article, the best solution would be to bring it up there, rather than unlink all the pages that link to it. I'm not saying you're wrong; I haven't looked at the article yet, I'll do that. --Chetvorno^TALK 22:17, 12 June 2014 (UTC)

Please look at the talk pages when you do. You may agree it is unnecessary to note the problem there. Macdust (talk) 00:21, 13 June 2014 (UTC)