Talk:Capacitor/Archive 2

message: 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)
thread_title:  Trimpots 

message: 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)
replies: text: 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)
thread_title:  Stored charge or energy? 

message: 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)
thread_title:  Recent edits by 24.12.159.248 

message: 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)
thread_title:  Capacitor vs Capacitance 

message: 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)
thread_title:  Field-theoretic items 

message: 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)
thread_title:  Definition of capacitance in words 

message: 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)
thread_title:  Transfer Function 

message: 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)
replies: text: 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)
thread_title:  Re-factor to "Electrolytic capacitor"? 

message: 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)
thread_title:  Capacitor type vs. frequency 

message: 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)
thread_title:  Condenser 

message: 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)
replies: text: 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)
thread_title:  Who coined the term "battery" ? 

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

message: 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)
replies: text: 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)
thread_title:  Electrolytic capacitor explosions 

message: 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)
replies: text: 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)
replies: text: It sounds like adhesive staking material.--Asher196 (talk) 02:31, 31 March 2011 (UTC)
thread_title:  White material around base of capacitor 

message: 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)
thread_title:  AC use 

message: (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)
thread_title:  Why there is a phase shift between current and voltage in a capacitor 

message: 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)
thread_title:  More History 

message: 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)
replies: text: 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)
replies: text: 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)
replies: text:  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)
replies: text: (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)
replies: text:  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)

text: 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)
replies: text:  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)
replies: text: 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)
thread_title:  Electrolytics in Series for AC 

message: 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)
thread_title:  Shocking Quotes Incorrect 

message: 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)
thread_title:  Capacitors in Series for HV 

message: 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)
replies: text: 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)

text: 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)
thread_title:  Fallacy 

message: 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)
thread_title:  Noise Filters and snubbers 

message: 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)
thread_title:  DC circuits plot 

message: 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)
replies: text: 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)
thread_title:  Electroluminescent (EL) wire 

message: 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)
replies: text: 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)

text: 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)
thread_title:  Back to back electrolytics 

message: 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)
replies: text: 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)
thread_title:  DC circuits equation 

message: 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)
thread_title:  Wakefield experiment 

message: 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)
thread_title:  Add Voltage Coefficient to Non-Ideal Behavior section 

message: Please see the corresponding discussion thread at Wikipedia talk:WikiProject Electronics. Thanks! • Sbmeirow • Talk • 23:34, 15 December 2013 (UTC)
thread_title:  Request for Discussion of {{tn|Semiconductor packages}} in electronic articles  

message: 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)
replies: text: Indrek (talk) 11:54, 31 March 2014 (UTC)
thread_title:  Semi-protected edit request on 31 March 2014