Wikipedia:Reference desk/Archives/Science/2017 July 8

= July 8 =

Is that true that things which plugged in consume electricity while they don't work?
I've been told that things that are plugged in, consume electricity even while they don't work. For example kettle, oven, or even just a phone charger which plugged in, while it's without the phone. Is that true? If it is, then for me it doesn't make sense and I would like to know the explanation behind it. 5.102.253.81 (talk) 03:05, 8 July 2017 (UTC)
 * Many electronic devices such as televisions, do draw a trickle of current to maintain readiness when switched on. But 'dumb' devices such as toasters, electric ovens and so forth generally don't. You can buy a current tester at the hardware store to check how much electricity is flowing when a device is nominally 'off' if you worry about these things. Abductive  (reasoning) 03:34, 8 July 2017 (UTC)
 * See our standby power article for more information. DMacks (talk) 03:35, 8 July 2017 (UTC)
 * And such "vampire" devices which use standby mode are an increasingly large proportion of all consumer electronics. Unless all current is cut to the device or a diagnostic forces a restart, most such items never de-power their built-in computers--which were traditionally very simple but which now have increasingly complicated tasks, not the least of which today is networking with other devices and (increasingly), the internet of things.  Most consumer electronics are moving towards a design where they are almost never completely "off", nor even off in a significant sense.  Many still give an impression that something drastic changes when you hit the power button, but the reality is that the difference between being "on" and being in "standby mode" for some devices is no more significant than the status of the indicator lights on the device's exterior: the device is still communicating with other devices and/or a network or even an internet connection, and is just as prepared to do what it is designed to do as it would be at any other time.  Still, for larger appliances, these standby functions of the computer and antennae are likely to represent a small amount of power consumption compared to the energy utilized when the appliance is performing it's nominal function.  Even so, there are concerns about the aggregate amount of extra power that is being utilized (and arguably wasted in many cases) by vampire electronics as they become more and more prevalent.  S n o w  let's rap 18:23, 8 July 2017 (UTC)
 * 'dumb' devices such as ... electric ovens .. generally don't. — Very old electric ovens don't, but I suspect that any electric oven built in the last few decades includes an electric clock, which always draws some current. Mitch Ames (talk) 12:42, 8 July 2017 (UTC)
 * And very soon, I doubt there will be an oven built for mass manufacture anywhere in the world that doesn't have a (relatively) sophisticated computer. I imagine an oven is one of those devices that manufacturers will begin to add network capabilities to last, because of liability concerns (the idea that an oven can be turned on remotely, and thus be susceptible to hacking or command errors must be a concern for even those companies which are moving aggressively on making their devices network enabled by default), but (at least when in the first world) I have rarely seen an oven in the last decade that does not have some degree of programmable function.  S n o w  let's rap 18:36, 8 July 2017 (UTC)
 * (ec)To use electricity there has to be a completed circuit. Any appliance with something going on while powered off, such as a clock, will consume electricity. More details are in Standby power. ←Baseball Bugs What's up, Doc? carrots→ 03:36, 8 July 2017 (UTC)
 * Charging devices often draw some current even when nothing is connected to them. This happens because they contain transformers, which allow for a completed circuit on the input side even if there is not a completed circuit on the output side. However the null current is usually very small, in the milliwatt range. Looie496 (talk) 14:41, 8 July 2017 (UTC)
 * ... and the same applies to modern switch-mode power supplies used for charging.  D b f i r s   16:11, 8 July 2017 (UTC)
 * Plugging in even an appliance with its mains switch at OFF causes a small AC current to flow in the capacitance between its power conductors. This happens throughout the cables of a network and AC generators experience a significant capacitive load when driving long distribution lines. However this reactive current leads the voltage cycle by 90 degrees and therefore does not contribute to the measured "true" AC power consumption given by P=VI cos φ, see Wattmeter. An electricity supplier charges only for true power consuption but could in principle detect whenever you plug in an appliance by time-domain reflectometry. An advantage of a DC distribution system over AC is that there is no continuous current in cable capacitance, only a one-time inrush at start-up. Blooteuth (talk) 18:01, 8 July 2017 (UTC)
 * Kindly look up the capacitance of, say, a 2 meter appliance cord, calculate the reactance, and the current flow, estimate the resistance downstream of the meter through which the miniscule current will flow to use up metered power, then state what the power bill would be per century per appliance. It is negligible. DC versus AC is irrelevant in this case. Edison (talk) 03:01, 13 July 2017 (UTC)
 * One rule-of-thumb is that if the plugged-in device gets hot, or even warm, when not in use, then it's using lots of electricity. The temperature is measured relative to the surroundings. StuRat (talk) 18:15, 8 July 2017 (UTC)

If humans never cut their hair, then will the hair insulate the body like fur?
Non-human animals don't wear clothes. Mammals may have fur to keep warm. If humans never cut their hair, then will the hair insulate body heat and cover the genitals? In other words, can long hair do away with the need to wear clothes? Also, I remember watching a King Kong movie and Jumanji, and I noticed the bearded men just shaved off their beard. What's the deal? Why do humans shave off their hair? 50.4.236.254 (talk) 04:04, 8 July 2017 (UTC)


 * 1) No, human hair is just too thin to provide insulation anything near what clothes can provide. We don't have polar bear hair.


 * 2) Shaving a beard may make hygiene easier (no food collecting in the beard) and make emotions more obvious if smiling and frowning weren't visible before. It also can make the man cooler in summer and avoid icicles forming in it in winter.  Then there's just style and cultural or personal preference. StuRat (talk) 05:30, 8 July 2017 (UTC)


 * Did you actually bother to read Body hair or Beard before coming here, 50.4.236.254? {The poster formerly known as 87.81.230.195} 90.211.129.9 (talk) 05:40, 8 July 2017 (UTC)


 * It does not talk about fur. It does mention furry mammals, but still, humans today still have hair. It may not be as numerous as before, but it's not labeled as fur. 50.4.236.254 (talk) 11:48, 8 July 2017 (UTC)


 * Humans don't have fur. ←Baseball Bugs What's up, Doc? carrots→ 12:17, 8 July 2017 (UTC)


 * A thick head of hair does provide a bit of protection against cold or against sunburns of the scalp, although not substantially... As for the rest of body hair, it's less effective than the adipose/fat tissue under the skin.  — Paleo  Neonate  - 12:50, 8 July 2017 (UTC)


 * Does this mean that humans with more adipose tissue have an easier time staying warm during the winter but harder time staying cool during the summer than humans with more muscle mass than fat mass? 50.4.236.254 (talk) 14:10, 8 July 2017 (UTC)


 * They said hair provided some protection from sunburn so there is no implication that way in what has been said. Please read adipose tissue which discusses adipose/fat tissue further. Dmcq (talk) 14:58, 8 July 2017 (UTC)


 * PaleoNeonate did also say "As for the rest of body hair, it's less effective than the adipose/fat tissue under the skin" so they did raise adipose/fat tissue insulation issues although didn't imply insulation works the way the IP seems to think it does. I agree the IP really needs to learn to read more rather than just asking whatever crap comes to their head, presuming they really aren't trolling which is getting harder and harder to believe. Nil Einne (talk) 15:36, 8 July 2017 (UTC)


 * What kind of questions do you expect or want to see? 50.4.236.254 (talk) 16:04, 8 July 2017 (UTC)


 * From you? Probably none would be the best solution. If you can't help it, at least put some basic thought and preferably reading/research before asking stuff like "Is there a governing body for astronauts? Are they excused from paying taxes? How are food resources used? Do they have families in space too?" Nil Einne (talk) 17:40, 8 July 2017 (UTC)


 * Long hair is nice but it doesn't extend indefinitely - there is a catagen cycle where hairs drop out, which usually doesn't let it get to storybook lengths. But we do have a picture in that article of a German model with some really long hair -- I don't know how she does it. Wnt (talk) 15:37, 8 July 2017 (UTC)


 * We should discuss some of the advantages of clothes over thick fur/hair. They allow us to select whatever clothes are appropriate for that day or even portion of the day, while fur/hair can't be changed nearly so quickly.  So, while animals may have a summer coat and a winter coat, we can adjust our level of insulation based on the daily weather, can select waterproof or water-resistant clothing when rain is expected, and can clean or replace our clothing when it's dirty or damaged.  Compare this to how a cat cleans it's fur with it's tongue, regularly resulting in hairballs, and you can see how much better clothing is.  Also, fleas and ticks are more of a problem for animals with thick hair and fur.  Sweating is more effective for cooling with bare skin, although some animals, such as horses, sweat with thick coats of hair.  Military camouflage can also be changed quickly when it's in the form of clothes, versus hair or fur.  Note that the most flexible camouflage in nature is from bare-skinned animals, such as cuttlefish and chameleons.   There's also a range of special-purpose clothing, like a dry suit, chem suit, and astronaut's suit. StuRat (talk) 20:15, 8 July 2017 (UTC)
 * There is a myth among short-haired people that long hair is hot in the summer, but nothing could be further from the truth. The way hair lays allows an outer layer to take the brunt of the sunlight, while a lower layer wicks sweat from the body and stays cool.  (In many other animals these layers are specialized, with guard hairs for the former function).  Without hair, the sweat just drips off all over, a mostly useless waste of water. Wnt (talk) 10:05, 9 July 2017 (UTC)
 * Depends a bit on the type of hair. Afro-textured_hair discusses how this is considered to be the type of hair all our ancestors had, and indeed provides a cooling effect. Various other types of hair developed in colder climates most likely have subtle differences in total insulation/air circulation effects. SemanticMantis (talk) 15:06, 9 July 2017 (UTC)

Digital audio: any advantage for whole number of cycles?
In digital audio, is there any advantage -- other than the computational optimization when synthesizing -- to using sound waves whose period is a whole number of samples (e.g. 441 Hz instead of A440 on a CD, since the sample rate is 44100 Hz)? I ask because 44100 is 2²3²5²7², which suggests a particular septimal tuning if the answer is yes. Neon Merlin  13:52, 8 July 2017 (UTC)
 * Theoretically there is no advantage —– the Nyquist–Shannon sampling theorem says that a sampling rate of 44100 Hz will perfectly capture any signal made up of frequency components below 22050 Hz. However if the program cuts corners in its signal processing algorithms, it is hard to rule out effects. Looie496 (talk) 14:32, 8 July 2017 (UTC)
 * A very simple monophonic tone Synthesizer for Electronic music is based on frequency dividers fed by a single oscillator. This allowed an early use of the speaker in the IBM Personal Computer to generate waveforms using the programmable interval timer. However division by whole numbers of clock cycles restricts the available frequencies so that Septimal tuning is possible but the conventional (in the West) Equal temperament tuning where successive note frequencies are in the ratio 12√2 ≈ 1.059463 can only be approximated. Modern digital music synthesizers use DSP techniques to calculate the amplitude of each sample in the time domain, and the stream of digital samples passes to a Digital-to-analog converter followed by a low-pass Reconstruction filter that removes the spurious effects of whatever finite sample frequency was used, see Whittaker–Shannon interpolation formula. Blooteuth (talk) 16:16, 8 July 2017 (UTC)

Lizard Identification
Looking to identify this lizard spotted on a tree in Home Depot parking lot in Stuart, FL. I suspect it is invasive / exotic pet. https://www.flickr.com/photos/somedumbaddress/35669273661/in/datetaken/ Thanks! — Preceding unsigned comment added by 2602:306:C4D5:DF60:FD57:922B:4DC7:DB82 (talk) 18:53, 8 July 2017 (UTC)


 * Looks like a Knight anole, which are native to Cuba but have been widely introduced to South Florida, which includes Stuart, Florida. StuRat (talk) 20:28, 8 July 2017 (UTC)


 * Yep, looks like that to me too. Certainly some type of anole, and the size and head shape do look like the Knight. SemanticMantis (talk) 15:02, 9 July 2017 (UTC)


 * Thanks, I think your ID is correct. I hadn't checked through the Anole family because I assumed they were all much smaller, like the more common Brown and Green Anoles.  — Preceding unsigned comment added by 2602:306:C4D5:DF60:FD57:922B:4DC7:DB82 (talk) 17:13, 9 July 2017 (UTC)


 * You're quite welcome. StuRat (talk) 15:50, 11 July 2017 (UTC)

StuRat (talk) 18:59, 10 July 2017 (UTC)