Talk:Incandescent light bulb

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Efficiency and environmental impact[edit]

I've made the following changes to the first section of "efficiency and environmental impact"

  • Clarify the difference between radiant luminous efficacy (LER) and source luminous efficacy (LES)
  • Specify the values in the table that are LER and LES
  • Removed the LER of "white light" as 240 lpw, since the white light source was not defined, and it REALLY must be.
  • Removed the reference for the two idealized sources at 4000 and 7000 K, since it was not relevant to the values given. I believe the value for the 4000 K source is incorrect, it should be 8% and 55 lpw, but I have not changed the values.
  • Corrected misuse of "efficiency"
  • Replaced 3683 as the melting point of tungsten with 3695, as per theTungsten article.

PAR (talk) 04:44, 14 May 2012 (UTC)

This section begins with the statement "Approximately 90% of the power consumed by an incandescent light bulb is emitted as heat, rather than as visible light ..." This is at odds with the figures in the table below in this section and with the statement in the third paragraph of the introductory section that "most incandescent bulbs convert less than 5% of the energy they use into visible light." I've rewritten the sentence as "Of the power consumed by typical incandescent light bulbs, 95% or more is converted into heat rather than visible light ..." Piperh (talk) 17:55, 5 November 2013 (UTC)

I think the confusion stems from the fact that the section jumps right into "luminous efficiency" and "efficacy" without first describing plain-old, straight-forward "conversion efficiency." Conversion efficiency is amount of total emitted radiation per the total electrical energy used. For a 120 volt, 100 watt, gas-filled lamp, this is about 10%, according to the books I've read.
One of the problems is that nearly all the light --even visible light-- is eventually turned into heat energy. The only energy not wasted is the tiny amount that actually falls upon the retina. The rest just bounces around the room until it is all absorbed or flies out the window. It might be helpful to know where all the energy is all going, rather than saying it is just heat.
As I understand it, the blackbody radiation from the filament is typically centered in the mid to far IR. The IR cut-off for the glass is typically around 1500 to 2000 nanometers, so any radiation longer than this wavelength is absorbed by the glass. The total conversion efficiency (total radiation output/watts) is indeed ~10%. (This includes UV, visible, and near-IR.) The rest of the radiation is absorbed by the glass and re-emitted as convection or radiation of a much lower wavelength. Some energy is also wasted as thermal conduction from the filament, or lost in the wiring and connections, or is just a victim of pure entropy. (Interestingly enough, I saw on Nova yesterday that a 120 volt, 100 watt incandescent bulb will put off the same amount of light when operated on just 12 volts, provided that the wiring is cryogenic superconductors.) It might be helpful to briefly explain something about conversion efficiency before defining luminous efficiency and efficacy, and explaining why it is lower (less than 5%). (Just a thought.) Zaereth (talk) 02:47, 7 November 2013 (UTC)
It might also be useful to explain how lamps of higher wattage become more efficient. (If I remember correctly, beyond 1500 watts, incandecent lamps become much more efficient.) Also, if you live in cold environment, like mine, the emitted heat is not necessarily wasted, because it has a direct effect on my heating bill. Zaereth (talk) 02:57, 7 November 2013 (UTC)

"When used for lighting in houses and commercial buildings, the energy lost to heat can significantly increase the energy required by a building's air conditioning system, although during the heating season such heat is not all wasted, but is not as effective as the heating system." is a very biased characterization of the article cited. The article's author goes on to say "As always, of course, there are some exceptions that may just prove the rule. Most notably, as Paul Wheaton demonstrated in his excellent video on heating the person, not the house, task lighting using an incandescent bulb and a shade/reflector can act as a useful heat lamp, providing heat exactly where it is needed and not warming up the surrounding air. In fact, it's something I'm considering deploying in my own efforts to heat my home office efficiently." — Preceding unsigned comment added by (talk) 19:35, 16 April 2014 (UTC)

Did you know...[edit]

Noting the bit about bulbs having fusible lead-in wires to avoid the bulb drawing a large current when the filament fails and an arc is formed, I suspect any current so formed will be less than the current needed to blow a hole in the metal cap when the live lead-in wire breaks freeing one end to make contact with the earthed cap. Perhaps the article can be expanded on the lines that the fuses can be pointless as they themselves can draw a greater current when they fail! I've even photos of such blow-holes in the sides of bulb caps - somewhere.

In actual fact: if the bulb contained a vacuum, then the parting filament wires will not produce much in the way of an arc. In a perfect vacuum, of course, there will be no arc at all as there is nothing to ionise. However, in a gas filled bulb, the arc formed when the filament parts can and often does ionise a significant part of the gas filling. This creates a momentary short between the filament lead in wires. It is the main reason why the failing bulb gives a bright flash. It is this current that ruptures the in built fuse, and sometimes the circuit feed fuse. In the early 1960's, in Britain, there was a brief fetish with installing high speed fuses in distibution boards. It was unknown for a failing incandescent bulb not to take out the circuit fuse as well. Vacuum bulbs (which were still available in some sizes) were imune from this effect.

In march, 2014, in Canada these light bulbs will be phased out. (talk) 21:51, 17 January 2014 (UTC) (talk) 15:51, 2 October 2012 (UTC)

Edit request on 5 November 2012[edit]

I wanted to edit it by myself, but page is protected. Please edit table "Comparison of efficacy by power" and include 230Volt light bulbs also. So one can compare differences between 120Volt and 230Volt lights sources. Dusan Hlavaty (talk) 09:48, 5 November 2012 (UTC)

If you can provide the details for the alternative voltage bulbs which you wish to add - and a reliable source for the data, please reactivate this request, so that someone may add your information.
Thanks. Begoontalk 10:54, 5 November 2012 (UTC)

EDIT: OK, I was trying to update "Comparison of efficacy by power" table like this: (All values are well known, because these bulbs are typically available in stores. I cannot find any reasonable source for other wattages like 35 Watt, 55 Watt, ...)

Comparison of efficacy by power
120 volt lamps[1] 230 volt lamps[2]
Power (W) Output (lm) Efficacy (lm/W) Output (lm) Efficacy (lm/W)
5 25 5
15 110 7.3
25 200 8.0 206 8.24
40 500 12.5 330 8.25
60 850 14.2 584 9.73
75 1,200 16.0
100 1,700 17.0 1,160 11.6
150 2,850 19.0
200 3,900 19.5 2,725 13.62
300 6,200 20.7 4,430 14.77
500 7,930 15.86


  1. ^ Wells, Quentin (2012), Smart Grid Home, p. 163, ISBN 1111318514, retrieved 2012-11-08 
  2. ^ Roy, Kamesh (2006), Illuminating Engineering, p. 30, ISBN 8170088984, retrieved 2012-11-07 

Ok - thanks very much indeed for doing that. I'm going to leave this request open for others to comment on, though, because I'm not comfortable adding so much unsourced data (noting indeed that the original table is itself unreferenced.)
I think I'd like to see some consensus that we should be adding more uncited data, and that it will improve the article to do so. I'm afraid I don't have enough information to know whether these numbers are reasonable or not, sorry.
Thanks again for presenting all this - hopefully some other editors can share their opinions. Begoontalk 09:49, 6 November 2012 (UTC)
If it helps for a reference, a chart showing 230V Incandescent lamp efficacy can be found in this book, Illuminating engineering on page 30. Zaereth (talk) 20:56, 7 November 2012 (UTC)
Thank you Zaereth. I've combined that data in the table above. Are we happy to edit the page with this table, leaving the original data as {{cn}}? Begoontalk 23:42, 7 November 2012 (UTC)
You're welcome. For a ref for that, the numbers seem to very closely match the numbers in a chart found in this book, Smart Grid Home on page 163. However, the book doen't actually say what the input voltage is. I found a 1961 version of the IES Lighting Fundamentals Course which gives a similar chart, showing both 120 and 230V efficacy, on page 21, under a section titled, "Why is it preferable to operate incandescent lamps on 120-volt circuits rather than on higher voltage circuits?" It's almost identical to what we have here, but is not available on google books. All in all, I'd say we seem to have it right. Zaereth (talk) 00:28, 8 November 2012 (UTC)
Great - well, I'd say those figures come from the same place ours do, where they exist they are a perfect match. So - removing the unsourced rows, we now have the new table above, which I think is perfectly adequate, and fully sourced. Begoontalk 01:06, 8 November 2012 (UTC)
I forgot to mention - the first 2 paragraphs on that page (163), in the section preceding the table, seem to clearly indicate to me that the table relates to 120 volt bulbs. Begoontalk 01:29, 8 November 2012 (UTC)
You're correct. I didn't read the paragraphs above the heading, but had almost mentioned something similar in my earlier comment, that is, nearly all incandescents are 120 volt. That, along with the similarity between his numbers and ours, seem to imply that the chart is indeed 120 volt. I think you've done a good job on our chart. If no one else has any objections, I'd be happy if you put the new chart into the article. (I'd do it myself, but am no good with graphics, templates, or other compuetr stuff.) Zaereth (talk) 01:38, 8 November 2012 (UTC)
Done then, with this copy/paste edit. Thank you.
Incidentally, I hate wikitables, they are horrid things, but I write a lot of code in my day job, so I can tolerate it. Begoontalk 02:04, 8 November 2012 (UTC)

How did these references get in, it is obvious they don't belong : ^ "Storey's guide to raising chickens" Damerow, Gail. Storey Publishing, LLC; 2nd edition (12 January 1995), ISBN 978-1-58017-325-4. page 221. Retrieved 10 November 2009. ^ "277 Secrets Your Snake and Lizard Wants you to Know Unusual and useful Information for Snake Owners & Snake Lovers" Cooper,Paulette. Ten Speed Press (1 March 2004), ISBN 978-1-58008-035-4. Page 161. Retrieved 10 November 2009. — Preceding unsigned comment added by (talk) 16:30, 6 April 2013 (UTC)

I find it very curious (and I'm an EE) that efficiency is different for the same wattage bulb at different voltages (designed for that voltage), someone mentioned a reference above so maybe its plausible but an explanation would be appreciated. — Preceding unsigned comment added by (talk) 06:55, 14 May 2013 (UTC)

Health issues[edit]

I don't see the point of the Health Issues section at the end. The problems mention refer to fluorescent bulbs, not incandescents. It seems as if someone was trying to make a point (POV) that CFL bulb light may be harmful to health. That may be so, but it doesn't belong here. I'll check back later, and if no one has objected, I'll delete the section. MarkinBoston (talk) 01:58, 20 December 2012 (UTC)

May 20 edits[edit]

Could somebody with editing rights please review edits by Apteva (currently blocked)? Some edits were genuine link improvements while some were stealth edits changing complete meaning of sentences without any supporting references and, quite frankly, just garbage insertions. Thank you. (talk) 14:21, 29 May 2013 (UTC)

I have reviewed the changes made and can see nothing wrong with any of them. He removed an uncited claim that has been tagged for 5 months (No problem). He clarified that the life of a CFL is "up to" 10,000 hours not just 10,000 hours (No problem because even the lamp manufacturers state "up to" in their lifetime claims). And he added a link to the Pheobus cartel which was already referenced and linked earlier in the article (So no problem here either).
It might help if you indicated which edit(s) you have a problem with and why. I don't understand your point about "stealth edits". It is impossible to make a stealth edit in Wikipedia because all adits, and who made them, are visible to everyone in the edit summary. –LiveRail Talk > 12:03, 30 May 2013 (UTC)

Bioluminescent Bacterial Lightbulb[edit]

Here is a recent discovery news article on an electricity free light bulb that uses genetically engineered bacteria; would this be the correct article to mention it? [1] CensoredScribe (talk) 21:20, 29 September 2013 (UTC)

It doesn't sound like it's an incandescent bulb, and it hasn't actually been produced successfully in significant quantities (and thus has no reasonably foreseeable impact on the market for incandescent bulbs), so I don't think so. —BarrelProof (talk) 17:45, 29 September 2013 (UTC)

Citation needed[edit]

A citation is needed for the sentence: "Heat from lights will displace heat required from a building's heating system, but generally space heating energy is of lower cost than heat from lighting." CozmicCharlie (talk) 20:58, 16 December 2013 (UTC)

If the building has electric resistance heat, then the space heating cost would be the same. If the heat is from fossil fuel, then the space heating energy would be more expensive. If it is solar heat, then the heating energy might be cheaper. I do not see the need for a citation for the obvious, but it should not be difficult to find a ref. I will take a look in the next few days. Edison (talk) 21:13, 16 December 2013 (UTC)

Section "Commercialisation" - 'granted British Patent No 8 in 1880'.[edit]

I can't believe this is correct, even with the referencte (which I can't check). Is "The eighth patent issued in 1880" meant? I can't believe it was the eigth patent ever issued in the UK, especially later in the section it says the same patentee got Patent 4933 in the same year. Can anyone check this? Si Trew (talk) 19:05, 6 January 2014 (UTC)

I don't have access to the source, but I do think this may be a typo. I don't have access to the actual patent either. However, the book A to Z of STS Scientists by Elizabeth H. Oakes (available on google books) says it is patent number 18, not 8, and a few other sites on the internet seem to confirm.
According to this website from the British Library, British patents prior to 1916 reset to "1" every year. So Swan's patent is merely the 18th (or 8th?) patent issued in 1880." Zaereth (talk) 20:00, 6 January 2014 (UTC)
Thanks. Yes, on the edit summary I suggested it should be "8th [British] Patent] of 1880". Your ref seems better than what we have, but we could finesse it by saying "a patent of early 1880", or just "an 1880 patent". Having patent no. 1 might be interesting in its own right, but patent no. 8 isn't particularly interesting in its own right unless it could be clicked through to look it up; but I don't believe they're available (yet) online from the Patent Office or whatever it's now called. Si Trew (talk) 07:31, 7 January 2014 (UTC)
Ok, after looking into this deeper, I'm getting a lot of conflicting information from various reliable sources. I've checked a lot of books on google books. There are basically two stories which I can find. Either 1.) Swan received his first patent in 1878 or 2.) He recieved it in 1880.
All sources seem to agree that a patent was issued in November of 1880. Nearly half of the books say this was his first patent, and nearly half say it was his second. For the latter, the story goes that he was granted a patent in May of 1878, and then Edison was granted a patent in 1879, resulting in a law-suit. By 1880, Swan filed for a patent on an improvement,and then by 1881, Swan had joined forces with Edison.
The idea that the patent number is either 8 or 18 seems to be a complete falsehood. Perhaps it has something to do with the date, May 18th, which keeps coming up. (By both May and November of those years, one would expect the patent numbers to be into the thousands.) Adding to the confusion, the same source used for this article is used in the Joseph Swan article, but that article says something completely different, so I have no idea what the source really says. I agree that we should probably remove the patent number, until the actual patents become digitized and available online. I'm not sure there is any other way to sort out the confusion without simply picking the secondary source which we like best. Zaereth (talk) 21:34, 7 January 2014 (UTC)
With this edit I've finessed it to "a British patent of 1880", but I've kept the ref and the {{dubious}} tag for now (it may still be wrong, perhaps we should say 1878 or 1880, but that's a bit weasely). I doubt I could do more or better research than you, so I think it's really your call. Si Trew (talk) 08:14, 8 January 2014 (UTC)

Section "Power" (7.1), "Standard" bulb is not (in the UK: Pearl[escent]?)[edit]

The last sentence in this section reads:

Note that the lumen values for "soft white" bulbs will generally be slightly lower than for standard bulbs at the same power, while clear bulbs will usually emit a slightly brighter light than correspondingly powered standard bulbs.

Now perhaps I am being thick, but the second half of this sentence "while clear bulbs..." just repeats the first part, inverted, and should be cut. But I don't know what is meant by a "standard" bulb is; if "clear" is meant, then it should say so, not say "clear bulb" and "standard bulb" if they mean the same thing (this elegant variation is annulled anyway by the repetition in the second half of the sentence). Similarly I think what are called "soft white" bulbs in the article would be what we call "pearl[escent]" bulbs in the United Kingdom?

Perhaps the article could say e.g. "coated" bulbs instead of "soft white" (or "pearl"), but this is a bit vague since all bulbs are coated in several ways for other reasons. "Pigmented" or "colo[u]red" doesn't seem right either. Other editors have probably got better terminology than I can think of.

SO, may I suggest as a first attempt at a rewrite:

"Soft white" or "pearlescent" bulbs will generally be slightly dimmer (have lower lumen values) than clear bulbs of the same power rating.

However I am sure someone else can do better than that (which is why I have not changed it in the article myself).

By the way I think this article is extremely well written, informative and at the right level of expertise in general, it's a credit to its editors and to Wikipedia.

Best wishes Si Trew (talk) 08:00, 7 January 2014 (UTC)ow

Ah, I think I see my confusion. There are soft white bulbs, then standard (pearlescent) bulbs, then clear bulbs. If my assumption is correct then the sentence is not repetitive, but calling pearl[escent] bulbs "standard" is not a term I've heard used in the UK, so perhaps needs to be explained somehow. Si Trew (talk) 08:25, 8 January 2014 (UTC)

Cite error: There are <ref> tags on this page, but the references will not show without a {{reflist}} template (see the help page).