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Archive 1

Usage in car stereo equipment

I think the mention of the 1-farad capacitors for 1000W car-stereos is rather non-encyclopedic. And what is meant by "sufficient to drive"? Do these capacitors generate power? I suspect that the real answer is that by trial-and-error, someone has figured out that 1F capacitors can be used to stabilize the cars electrical system while playing typical (loud) music. That is, during the most powerful bass-bursts, the capacitor can feed current to the amplifier, and then be recharged until the next beat comes.

For how long?
They mention a Farad is a very alrge unit, but how large? They mention they can power 1,000 watt stereo, but for how long? Nnfolz 16:29, 9 February 2006 (UTC)
Not very, 1 farad means that when charged to 12V it will have 12 colombs of charge. I cba to do the calculus to work out how much energy that represents but it will be less than 144 (12*12) joules. so we are talking figures on the order of a tenth of a second or so. Still i can see it making quite a difference to heavy bass beats. Plugwash 01:22, 12 November 2006 (UTC)
I don't know what was removed but if putting in that femtofarad capacitors are used in integrated circuits, then putting in that 1 or more farad capacitors are used in car sound systems should be acceptable as a perspective tool. (A one Farad cap is about the size of a tennis ball can.) I've been researching capacitors as an alternative to batteries (yes I know that caps have 100x less power density/weight ration than bats), and I've seen these caps all over the net. It took me a while to figure out what (most) people use them for. I almost want to shell out the $100 for one so I can use it to explode walnuts and such :), although that would probably break the cap eventually. :(
Tiki God 15:29, 15 July 2007 (UTC)

Caps pic

I have added a picture of a 1F capacitor. If it is preferable to the existing one, maybe the existing one can be removed. —128.171.10.147 (talk) 02:50, 27 September 2007 (UTC)

How does Image:Supercaps_1.5F_capacitors.jpg‎ swing you? They are 1.5F, not 1F, though. - Keith D. Tyler (AMA) 19:37, 26 January 2007 (UTC)

I'd make the comment that the "puniness" that some complain of might not a function of capacitance but also rated voltage. Perhaps these people are really talking about the ability of the capacitor to store energy (0.5*C*V^2), which in turn is related to physical size and the amount of damage it can do when discharged? When discharged a 1pF capacitor charged to 1MV will do as much damage as a 1F capacitor charged to 1V, based on available energy. In fact the 1pF capacitor will probably discharge faster giving a higher instantaneous power. Maybe the complainer wants a pic of one of those high voltage capacitor banks used to power fusion reactors? :-) John Dalton 00:56, 14 March 2007 (UTC)

Added definition back

I'm not sure why the definition with equivalent units was removed a few days ago without a descriptive comment or Talk entry. I think this is necessary and useful information, and it is included in similar articles, such as Volt. I added it back with some tweaks. Edurant 05:44, 14 March 2007 (UTC)

Picture Detail

The description on the second picture which has the words "tricked-out car," has to be unnecessary. Re-wording it with "...fills the back seat of a car." Under most situations, people know that stock cars don't normally have large capacitors for a stock stereo (i.e. custom stereo systems = custom parts, stock stereo = stock parts). --Specter01010 02:53, 19 April 2007 (UTC)

Picture accurate?

That looks VERY small for a 1F capacitor 86.29.81.44 (talk) 07:04, 16 April 2008 (UTC)

I added clarification to the image. It is accurate, but it is a special type of capacitor specifically tailored to keep a low voltage for a very long time, to replace small batteries in areas where you want to keep a memory circuit or small micro controller powered. —Preceding unsigned comment added by 83.254.119.247 (talk) 22:01, 20 December 2010 (UTC)

This is about the capacitance unit of measure. For the charge unit, see Faraday.

Corrected the "Faraday" link from http://en.wikipedia.org/wiki/Faraday to http://en.wikipedia.org/wiki/Faraday_(unit) 77.127.68.216 (talk) 20:13, 24 June 2008 (UTC)

Coulomb

One coulomb of charge is 6.25e18 (6.25 * 10^18, or 6.25 billion billion) electrons. One amp represents a rate of electron flow of 1 coulomb of electrons per second, so a 1-farad capacitor can hold 1 amp-second of electrons at 1 volt.

SMalken 18 August 2008 202.1.53.80 00:26, 18 August 2008 (UTC)

Retrofit topic year headers

17-Sep-2008: I have added subheaders above as "Topics from 2005" (etc.) to emphasize the dates of topics in the talk-page. Older topics might still apply, but using the year headers helps to focus on more current issues. Also, new topics might be more readily added to the bottom, not top. Afterward, I sorted older topics into date order. -Wikid77 (talk) 05:04, 17 September 2008 (UTC)

Mentioned microfarad at the top

17-Sep-2008: I have been revising several articles tagged as "too technical" to focus for general readers. The term "microfarad" is very common, so I repeated it in the top paragraph, according to the Wikipedia style of including redirection terms in the top text, to reassure readers that their topic is covered by the article. For simplicity, it is good to mention the subtopics (such as "microfarad") near the top, so the reader doesn't see a "shaggy dog story" before their specific issue is addressed in the article. However, to off-load details, I inserted the phrase "(defined below)" to alert the reader to continued reading, without cluttering the top text with those sub-details. It is a balancing act: to mention sub-topics briefly in the top text, but then defer the actual sub-details until further in the article. -Wikid77 (talk) 05:18, 17 September 2008 (UTC)

Capacitance and Power

I added the conversion from power, time and voltage. I needed this to work out regen braking so I thought I'd add it too. —Preceding unsigned comment added by 81.174.174.31 (talk) 22:56, 3 March 2010 (UTC)

Definition

In the definition if says F = C^2/(Nm^2) and I believe it should be F = C^2/(Nm) Yes! The units of F = C^2/(Nm^2) is INCORRECT. It should be F = C^2/(Nm). —Preceding unsigned comment added by 72.33.56.74 (talk) 20:31, 7 July 2010 (UTC) The definition is 'F=C^2/(Nm) I am unable to see where it is defined at C^2/(Nm^2)? —Preceding unsigned comment added by Rickysz (talk • contribs) 14:27, 29 July 2010 (UTC)

I'm not sure that the relation to Voltage and Joules is stated correctly. Unless I missed something, F = J / (V^2) rearranges into J = F * (V^2) if you're trying to solve for J. However, many sources ( http://www.ebroadcast.com.au/lookup/encyclopedia/ca/Capacitors.html ) give this formula as J = (F/2) * (V^2). 60.242.28.67 (talk) 08:01, 15 February 2011 (UTC)

I agree. A number of the equivalences are wrong on this page. J = 1/2 * F * V^2, at the very least, which rearranges into F = 2 * J / V^2 Jonathan (talk) 13:53, 24 September 2011 (UTC)

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common sense

in everyday calculations the W.h is more common than J[oule]. battery charges are often expressed in A.h, caculatively, the Farad also can be said in S[iemens].h, and Henry in Ω.h; (and Wb as V.h) so what prohibits this?
Tabascofernandez (talk) 00:04, 15 July 2017 (UTC)

Confusing Notation

In Wikipedia article "Farad", the character "C" is used for the Electric charge. In the article "Capacitance", the same character "C" is used for Capacitance. This is confusing.

Regards, Boris Spasov (bspasov@yahoo.com). — Preceding unsigned comment added by 107.184.14.103 (talk) 05:46, 24 June 2018 (UTC)

Femtofarad

What about redirecting "femtofarad" to "farad"? Or creating a proper article? --Edcolins 20:48, August 21, 2005 (UTC)

By all means create a redirect. I don't know any anecdotes about femtofarads, so I can't help you to create a proper article! Somebody can convert the redirect to an article later on, if they want to. --Heron 20:55, 21 August 2005 (UTC)
Done. --Edcolins 21:12, August 21, 2005 (UTC)

SI multiples is unnecessary

the SI multiples table is ridiculously unnecessary. Do I have to explain why? Fresheneesz 01:08, 23 May 2006 (UTC)

I concur, it's just silly. Pdbailey 00:49, 26 September 2006 (UTC)
I agree. I just removed it. Edurant 05:42, 14 March 2007 (UTC)

alternate definition

I changed

  • "an alternate definition is that a farad is one ampere-second of charge at one volt" to
  • "an alternate definition is that a farad is the amount of capacitance that requires one second for a one ampere flow of charge to change the voltage by one volt."

I hope this is more understandable. (But I would prefer a cited definition from a good source). --76.209.28.72 18:51, 26 June 2007 (UTC)

Created

The article "Farad" was created on 8-September-2002 by long-term user Heron. -Wikid77 (talk) 05:04, 17 September 2008 (UTC)

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