Wikipedia:Reference desk/Archives/Science/2009 October 18

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October 18

Voltage drop in an extension cord

So, here's a break from relativity and black holes and all that high-powered stuff...

My "good" 14-ga, 100-foot extension cord wasn't really that good, and finally died today. Bought a new one, CostCo had 12-ga cords for less than 14-ga cords at the local home repair store. I swear that my leaf blower is running faster on the new cord than the old -- speed being indirectly perceived by the racket it makes.

(1) Is this actually possible, or am I suffering from too much observer bias? (2) Can I safely measure the voltage at the end of the cord with a simple V-O-A meter, just sticking the prongs into the outlet holes?

Thanks to the electricians in the audience! --DaHorsesMouth (talk) 01:09, 18 October 2009 (UTC)

Certain voltmeters are designed for probing high-voltage, AC sources. However, this is categorically not safe - even if you are a trained electrician, it is still not safe. But, there is an alternative - and a better one, actually.

First of all, you don't care about the "resting" voltage - there will be virtually no voltage drop unless the leaf-blower is on, since no (net) current is flowing through the extension cord. So, you need to measure the voltage when operating the leaf blower. Consider buying one of these plug-in outlet voltage monitors. They are much safer to use, and you can use them while operating the leaf blower - to see whether turning it on causes a voltage drop at the end of the cord. Nimur (talk) 01:15, 18 October 2009 (UTC)

Here's a digital one, for ~ $25. Nimur (talk) 01:22, 18 October 2009 (UTC)

Calculating from the values in American wire gauge, using the 14 AWG cable instead of the 12 AWG should introduce an extra resistance of 0.1874 Ohms. Assuming it's a 20 amp circuit, that means the voltage drop could be at most 3.748 volts, and is actually something less than that. So the voltage to the appliance is being dropped by only about 3% or less, which one wouldn't think would be noticeable. Extra resistance due to corrosion on the contacts of the old extension cord, however, could make a much bigger difference. Red Act (talk) 01:42, 18 October 2009 (UTC)

OK, that'll do nicely. Nimur, I promise not to do something patently stupid -- today.

Do a proper scientific experiment. Have a friend or family member operate the leaf blower - you stand at a suitable distance away with your eyes closed. They flip a coin and plug the leaf-blower either directly into the wall outlet or into the old extension cord without telling you which they did. Repeat the experiment 10 times. Can you reliably tell where the leaf blower was plugged in from the noise alone? Repeat the experiment with the new extension cord. (I'm fairly certain you won't be able to tell which is which at a rate better than chance - but if you can, you need a higher gauge wire for your extension cord.) SteveBaker (talk) 15:01, 18 October 2009 (UTC)

My experience, strictly unscientific although I have a good handle on my volts and amps, is that the connections at the ends of the wire to the plug and socket tend to be the weakest link; for instance, on a high load, they will get warm while the wire itself is still ambient temperature, and they will fail frequently, while the wire itself never does. Gzuckier (talk) 20:02, 18 October 2009 (UTC)

Not tried running an extension cord fully wound up on high load then (e.g. doing the ironing as a relative of mine did)? Nice fire. The wiring in them is often pretty rubbish and loss of power seems quite plausible to me. --BozMo talk 20:29, 18 October 2009 (UTC)

Yes, I've seen one melt when used coiled, but inductive impedance contributes when coiled. Dbfirs 21:28, 19 October 2009 (UTC)

Inductive impedance may contribute much less than you think because there is virtually no external magnetic field coupling to the extension cord which is a Balanced line unlike the conductor of a solenoid, and the AC power frequency is low at 50 or 60Hz. A lamp on the end of an extension cord does not get dimmer when the cord is coiled. Cuddlyable3 (talk) 23:08, 19 October 2009 (UTC)

I would expect to hear an easily descernible difference between a 12 gauge and a 14 gauge 100 foot extension cord when driving a motor rated near the stated limit for the 14 gauge cord. How many amps is the motor rated at at 120 volts? You could also use a splitter at the motor end of the cord to measure the voltage under load for the two cords, if you have such a meter and understand how to make voltage measurements safely. Edison (talk) 00:07, 19 October 2009 (UTC)

OP here. I marked this as {{resolved}} about 48 hours ago, as I had enough information. Baker: it's bad form to remove somebody's tag and signature. If you wanted to continue the discussion, fine, but next time Don't edit others' comments, except to fix formatting errors that interfere with readability. --DaHorsesMouth (talk) 02:22, 20 October 2009 (UTC)

Not trying to take sides, but so you know: there's an opinion that those "resolved" tags are a bad idea. See this discussion. —Steve Summit (talk) 03:14, 20 October 2009 (UTC)

Hychlorite?

[[:File:Clorox Bleach Bottle.jpg|right|thumb|150px|Dilute Sodium Hypochlorite! SteveBaker (talk) 14:53, 18 October 2009 (UTC)]]

I toured George Eastman's house today and in his bathroom was a bottle labeled "Hychlorite". After doing a search, I see that there's a Flickr image of the bottles. I never expected to see an image of the exact same bottle on the net but okay... What was this? The closest I can find here or on Google seems to be Hypochlorite. Are these the same thing? From what I gather, hychlorite was used as an anti-septic. Can anyone confirm this? Dismas|^(talk) 02:59, 18 October 2009 (UTC)

From this, it appears that hychlorite is another name for sodium hypochlorite. Red Act (talk) 03:17, 18 October 2009 (UTC)

Looks like Hyclorite was a brandname for a commercial sodium hypochlorite preparation. See TALK:Sodium_hypochlorite#Hychlorite_and_Zonite for a link that supports this. 66.102.199.179 (talk) 03:22, 18 October 2009 (UTC)

External Speaker Noise Problem

Very recently my external speakers (5.1) connected through its own amp, has started making really huge buzzing noise. The noise starts if I just turn on the speakers. I have tried disconnecting the audio in cables, but the problem persists. Any help ? —Preceding unsigned comment added by 59.93.204.61 (talk) 04:12, 18 October 2009 (UTC)

I'm no audio engineer but two things spring to mind - the first is inteference - have you plugged in/installed new appliances either nearby or on the same ring main as the speakers/amps? Try disconnecting them/switching off if so. Secondly could be poor connections - check all plugs and sockets, then look for loose wires or poor solder joints. Exxolon (talk) 04:26, 18 October 2009 (UTC)

To figure out if interference is the problem, try using the speakers in another part of the house, or in a different house altogether. If the problem goes away, next try moving the speakers around your house to identify when the buzz is the loudest, and that should lead you to the interference source.

Also, do these speakers have their own volume control ? I've had lots of trouble with the rheostats used to control volume levels, although an intermittent crackling when changing volume is more typical of that issue. If this is the problem, you can either replace the rheostat or bypass it, using the volume control at the source instead of at the speakers.

Another thought is the power supply. Does the power cord have a wall wart ? If so, maybe you need to replace that. If the power supply is internal, then it may be more difficult, but still possible, to replace. StuRat (talk) 13:46, 18 October 2009 (UTC)

Strictly from practical experience, buzz or hum in an amplifier almost always comes from a "bad" power supply. What this means can vary; the power supply unit may have experienced hardware damage (e.g. a capacitor that has fizzled via dielectric breakdown) or it might just be picking up EMI interference. Check for other "high power" equipment nearby (physically or electrically - sometimes things like the refrigerator can be far away but on the same mains circuit). Anything with a motor or compressor will create EMI and power fluctuations in the audible range; but so can a variety of other electronic devices like televisions and other amplifiers. If the noise is not "hum-like", check the signal pathway for any unusual wiring; consider switching to a digital audio connection; consider physically moving or changing the orientation of the wiring to avoid passing near sources of electromagnetic interference. Nimur (talk) 14:34, 18 October 2009 (UTC)

You might try threading the cable through a ferrite bead (you can buy them in good branches of Radio Shack for example). SteveBaker (talk) 14:48, 18 October 2009 (UTC)

From past experiecne. noise in an audio system implies a grounding problem. Edison (talk) 00:03, 19 October 2009 (UTC)

Regulation of cholesterol in blood

Hi everyone I am a little confused about how cholesterol levels are regulated. The article on Cholesterol says that fat intake, especially that of saturated fats, plays a large role in blood cholesterol. My question is why? Surely our bodies can choose not to convert the fat we eat to cholesterol? I realise that fatty foods contain cholesterol but if my understanding is correct our bodies produce cholesterol from fat as well - why would it do this if the cholesterol levels were already high enough? Can't the process be inhibited in some way? Thanks in advance for any contributions! RichYPE (talk) 10:29, 18 October 2009 (UTC)

When humans (and their primate ancestors) evolved, the problem of excess fat and cholesterol consumption was so rare that there was almost no evolutionary pressure to developed a mechanism for dealing with this problem, because the portion of people who were unable to pass on their genes due to high cholesterol was almost zero. Had we evolved from predators, instead of mostly herbivores who eat meat only on rare occasions, then perhaps such a mechanism would have been passed on to us. StuRat (talk) 13:33, 18 October 2009 (UTC)

True. It's very rare to see arterial disease in dogs and cats, even when they're grossly overweight from being fed a high-fat diet. On the other hand, since cholesterol is involved in regulating the fluidity of cell membranes, which is crucial, our bodies have evolved with an emphasis on avoiding ever being too low on cholesterol, without ever facing much evolutionary pressure to keep the levels down. Until now. Gzuckier (talk) 19:58, 18 October 2009 (UTC)

The trouble with comparing typical human conditions with similar things in animals is that most animals don't live long enough to exhibit the problems. A 14 year old human would probably not have noticable cholesterol problems no matter how bad his/her diet has been...and not many dogs or cats live much longer than that. If you had dogs and cats living until 50 to 60 years old - then their fatty, cholesterol-laden diets might well cause them similar problems to humans - but we'll never know. SteveBaker (talk) 11:32, 19 October 2009 (UTC)

I'm not convinced by that argument. Cats and dogs eat more relative to their mass/volume (due to the square/cube law), which ought to counteract the difference in lifespan. I don't know which factor would be larger, but it is worth noting that cats and dogs get other age related problems (arthritis, for example) at similar ages to humans relative to lifespan, not in terms of absolute age. --Tango (talk) 11:41, 19 October 2009 (UTC)

FWIW I am with Tango on that one. Vast swathes of age related diseases in humans (cancer for example) have significiant mortality in shorter lived mammals past child bearing age. Nothing is as simple as a kettle furring up and all creatures will have evolved to have mechanisms to push progressive illnesses on average to an age where they have less evolutionary impact. The fact we sit on sofas eating burgers (not that I eat burgers) for decades after we were evolved to die is to blame. --BozMo talk 11:46, 19 October 2009 (UTC)

I don't think I agree with your "evolved to die" time - there hasn't been a large change in when people die of old age. The increases in life expectancy are primarily due to a reduction in infant mortality. If you reached adulthood you would probably reach your 50s or 60s, often older, even before the birth of modern medicine. There is evidence that evolution has made changes to make us more successful in middle/old age (eg. the Grandmother hypothesis), so you can't blame age related problems on evolution not caring what happens to us after we've had our children. (Yes, I'm anthropomorphising evolution, it's just easier to express it that way. I know it isn't accurate.) --Tango (talk) 12:00, 19 October 2009 (UTC)

You are right of course on the Grandmother hypothesis, and I don't know enough about whether people 100,000 years ago really ever lived to their seventies (after child bearing in their late teens) to contradict that so I leave, a little humbled! --BozMo talk 12:09, 19 October 2009 (UTC)

British museum website suggests aged 35 to 40 as a ceiling for Iron Age man but with no real evidence. --BozMo talk 12:12, 19 October 2009 (UTC)

Look at the list of Roman emperors. A fair number of them seemed to live to 60 or even 70, despite the fact that they also had to watch out for assassinations. Googlemeister (talk) 20:31, 19 October 2009 (UTC)

Our maximum lifespan seems to have changed little from that of our hunter-gatherer ancestry (Weiss, 1981). Marlowe (2000) also states that average life expectancies are misunderstood. Low average life expectancies at birth among contemporary foragers are due to high infant and juvenile mortality rates; whereas female foragers aged 20 have a life expectancy of 20 - 30 years beyond reproductive maturation (Burton Jones et al., 1992). These claims might be slightly exaggerated depending on the age at which you set menopause. Various authors give a present day mean age of between 48 and 51 years (Rees, 2004; Velasco et al., 1990; Melges and Hamburg, 1977), but many others advocate 40 years of age (Schultz, 1969) and some do not specify the age at all. There is some fossil evidence which suggests that most individuals from our hunter-gatherer past did not live past 50, but many contemporary foraging cultures comprise individuals that live into their 70s and 80s (Hill and Hurtado, 1991). For reference please see grandmother hypothesis. Matt (talk) 15:06, 22 November 2009 (UTC)

Seedless pepper

I bought a red pepper at a farmer's market and it doesn't have any seeds. Is this a mutant or a new breed ? I'd like to grow more of these myself, but, of course, have no seeds to do so. Is there another way to make the existing pepper grow ? StuRat (talk) 15:07, 18 October 2009 (UTC)

See seedless fruit. --Tango (talk) 15:18, 18 October 2009 (UTC)

It's likely a result of cross-breeding and selection. Obviously consumers like seedless varieties for convenience - and farm supply companies like them because farmers cannot simply use some percentage of their crop to provide seeds to replant the next generation of plants. For you, it completely sucks because there is no way to grow another plant from the pepper itself. Your best chance would be to somehow getting a cutting from one of the original plants, using rooting compound and producing a new plant that way. If you bought it from a local grower, that might not be impossible. SteveBaker (talk) 15:57, 18 October 2009 (UTC)

See also F1 hybrid. But the seed would probably not have grown true to type anyway.--BozMo talk 11:49, 19 October 2009 (UTC)

LNB Power

Does LNB consume the power from the receiver and also send its signals on the same coaxial cable? If so, how usually is it implemented (I.e.: is it like modulating the filtered signals on the same DC power)?--Email4mobile (talk) 16:33, 18 October 2009 (UTC)

Yes, the cable carries both the DC power and the IF signal, with a DC block between the RF and power sections at both ends. See DC bias#Remote power. Tevildo (talk) 17:02, 18 October 2009 (UTC)

The use of signal cabling to carry power is also used in other applications, see phantom power. --Jayron32 18:38, 18 October 2009 (UTC)

... and USB uses the same technique. Dbfirs 19:44, 18 October 2009 (UTC)

No, USB has separate power and signal conductors - they just share a common ground wire. Tevildo (talk) 19:51, 18 October 2009 (UTC)

Sorry, you are correct. My error! Dbfirs 16:53, 19 October 2009 (UTC)

Erie Canal

What would happen if all the locks on the Erie Canal were opened at once? Is it dangerous that this could occur? TheFutureAwaits (talk) 18:41, 18 October 2009 (UTC)

There may be local flooding, probably not much of any other effect. The Erie Canal is no longer a contiguous water way; large sections have either silted over naturally or have been filled and paved over as roadways. Some sections are maintained as recreational waterways, and do see some boat traffic; other sections have been added to the more modern New York State Canal System and do see some commercial barge traffic. See Erie Canal. --Jayron32 18:51, 18 October 2009 (UTC)

thioketone thioester?

What do you call an ester where it's RCS2-R' rather than jus R-COS-R' ? John Riemann Soong (talk) 19:51, 18 October 2009 (UTC)

It's a dithioester. Someguy1221 (talk) 20:31, 18 October 2009 (UTC)

why is phenol toxic?

Is it because it's a good nucleophile? How does its toxicity compare to methanol? John Riemann Soong (talk) 20:02, 18 October 2009 (UTC)

I don't seem to have access to any relevant journals, but Burns Volume 32, Issue 4, June 2006, Pages 517-521 should answer the question based on the outline. Someguy1221 (talk) 20:39, 18 October 2009 (UTC)

That source mostly discusses skin burns from phenol, which it says are due to its "caustic and defatting (hydrophobic effect of phenol) properties." No more specifics. Without giving a mechanism, it also mentions "systemic toxicity and poisoning usually occur by skin absorption, the main route of entry for solid, liquid or vapor phenol; the result can be lethal" with seizures, coma, and dysrhythmia. Pulmonary complications can include tachypnea, pulmonary edema, bronchospasm, and stridor, which to my medical student ear sounds potentially fatal also. - Draeco (talk) 05:38, 19 October 2009 (UTC)

Is there any accessible reason based on its aromaticity? I mean, it's separate from why benzene is toxic, right? John Riemann Soong (talk) 00:34, 19 October 2009 (UTC)

Aromaticity affects solubility and other hydrophobic interactions, and also the stability/reactivity of the hydroxyl. DOI:10.1016/S0009-2797(00)00171-X suggests toxicity is related to a radical formed from PhOH. Toxicity is always an interesting issue, and often the result of dozens of complicated and/or inter-related effects (is tyrosine highly toxic?). DMacks (talk) 00:42, 19 October 2009 (UTC)

Isn't it a suspected carginogen or am I years out of date? --BozMo talk 11:51, 19 October 2009 (UTC)

Isn't everything? More seriously though phenol says it is so either you're both out of date or is still is. I think it's supported by the ref [1] although I only partially understood it Nil Einne (talk) 15:37, 19 October 2009 (UTC)

This paper suggests phenol is activated to form a free radical in cells and then this reactive phenoxyl radical will modify components of the cell such as proteins and DNA. Tim Vickers (talk) 18:55, 22 October 2009 (UTC)

Which population clock is better?

There are several of them. I assume that (unlike in the US Census) they add uncounted people, which would make up a lot of the disagreements, and error. Sagittarian Milky Way (talk) 21:02, 18 October 2009 (UTC)

They add people that don't get counted during censuses and they estimate growth rates and use them to add people born/subtract people that died since the last census. I don't think there is any way we can really say which is best. I expect the margin of error is big enough to contain any disagreement. --Tango (talk) 21:14, 18 October 2009 (UTC)

Most countries, I suppose; but it is archaicly illegal to do that for the official US Census value for America that determines representation. The US Census' version of the clock number would not be under that requirement though. Sagittarian Milky Way (talk) 21:54, 18 October 2009 (UTC)

A woman delivers a baby approximately every second. By now she must be sick of it. Cuddlyable3 (talk) 13:49, 19 October 2009 (UTC)

See Lilith... Tevildo (talk) 17:55, 19 October 2009 (UTC)

Why ? Cuddlyable3 (talk) 22:53, 19 October 2009 (UTC)

A cat breastfeeding another adult cat?

What causes a queen to breastfeed another adult cat? No, the cat who is suckling is not a larger kitten or the queen's offspring. The queen breastfeeds another cat and the two cats are not related. Surtsicna (talk) 21:25, 18 October 2009 (UTC)

Please provide a reliable source to document that this phenomenon actually occurs. Sounds dubious/bogus/made up. Edison (talk) 00:01, 19 October 2009 (UTC)

He may not have one. The questioner could have simply witnessed this unusual phenomena and been curious about it. APL (talk) 00:11, 19 October 2009 (UTC)

Grr. Phenomenon. --Trovatore (talk) 01:48, 19 October 2009 (UTC)

Funny. Wiktionary says that "Phenomena" is the plural of phenomenon, but Merriam Websters says that it's a nonstandard but "borderline" singular (with its own plural.). Huh. In the future I will try to restrict myself to the most commonly accepted written form. APL (talk) 18:48, 19 October 2009 (UTC)

phenomenon comes from Latin phænomenon from Greek phainomenon "that which appears or is seen", a noun derived from phainesthai "to appear". Plural is phenomena. Cuddlyable3 (talk) 22:47, 19 October 2009 (UTC)

Ostensibly classical, noteworthy dictionaries also define temperature with a secondary definition of an increase in temperature, sort of backing into the common usage of the word "temperature" when, in fact, the word "fever" would be appropriate. Ever since I saw that a few years ago, I ceased using dictionaries as sources of definitive wisdom. DRosenbach ^{(Talk | Contribs)} 14:52, 21 October 2009 (UTC)

Linguistic prescription, Linguistic description. If people are using the word 'temperature' to mean 'an increase in temperature', then that is what the word means when they use it in this fashion. Dictionaries are not sources of definitive wisdom because there is no definitive wisdom when it comes to language use: language changes. All a dictionary can do is record how words have been used, when, and by whom, and so offer advice on how to effectively communicate without people jumping on your usage. They shouldn't say a common usage is 'wrong', because if it is commonly used it is part of the language. 86.140.149.215 (talk) 17:23, 22 October 2009 (UTC)

Now can you tell me why my cat is still breastfeeding the neighbourhood's adult stray cats? Surtsicna (talk) 20:21, 22 October 2009 (UTC)

Adult cats I have known love milk , and there is no reason to suppose they would not like cat milk. It seems less likely the female would want to provide milk to an adult cat. Edison (talk) 00:55, 19 October 2009 (UTC)

OR. We had 3 kittens over a year ago, one girl two boys, and when the mother refused to let them nurse any longer they all started nursing on the girl. She sucked on her own nipple, and the two brothers also sidled up for some cuddle time. They eventually quit, and it never seemed like she was lactating, so I suspect it was a comfort issue rather than a "we totally want more milk" issue.218.25.32.210 (talk) 05:52, 19 October 2009 (UTC)

Don't male cats have nipples? Axl ¤ [Talk] 07:46, 19 October 2009 (UTC)

OR. Lactating mother cats are very tolerant of who sucks. Zoo keepers know this and often seek a lactating cat to be a wet nurse for a variety of orphaned baby animals. Cuddlyable3 (talk) 13:46, 19 October 2009 (UTC)

I've seen it. My own cat (who has just stopped breastfeeding her kittens) breastfed a stray cat several times. I have a picture of the suckling cat trying to grasp a nipple while my cat is sitting. The cat was lying and breastfeeding another cat as if it were her own kitten just seconds before I took the picture. I really don't have a reason to make this up; cats are known to breastfeed a variety of animals. I just want to know what made my cat breastfeed another adult cat. Surtsicna (talk) 18:02, 19 October 2009 (UTC)

This practice is known as beastfeeding. (Just joking.) Bus stop (talk) 22:54, 19 October 2009 (UTC)