Wikipedia:Reference desk/Archives/Science/2011 June 24

= June 24 =

What kind of clothing do workers wear when doing work on power lines?
To protect themselves from electricity I mean. Do they wear rubber boots? ScienceApe (talk) 01:01, 24 June 2011 (UTC)
 * Most Linemen were standard personal safety equipment: gloves, safety hat, etc. For linemen that work on the sort of very high tension wires where they need protection from the electricty itself, they wear a sort of chain mail suit which acts as a personal Faraday cage.  See this video.  But most linemen don't need that sort of protection.  The guys working in the cherry picker working on the lines running next to the road usually just wear a hard hat, gloves, and sturdy clothes. -- Jayron  32  01:19, 24 June 2011 (UTC)
 * (ec) Prepare yourself for a big surprise! They don't wear rubber boots -- they wear clothes made of steel wires. Amazing? Incredible? Well, what this does is, it allows the dangerous high-voltage electricity to flow around their body rather than through it. 67.169.177.176 (talk) 01:24, 24 June 2011 (UTC)


 * I don't know, but I bet they piss on the ground far less than the average person at that height above street level does (however low that percentage is normally already.) --188.29.15.168 (talk) 01:24, 24 June 2011 (UTC)
 * You betcha! If you piss on the ground when you have a 500 kV potential difference with it, you'll get charbroiled and won't even know what hit you. 67.169.177.176 (talk) 01:28, 24 June 2011 (UTC)


 * Not true; the urine breaks up into droplets. See MythBusters (2003 season).--Shantavira|feed me 06:08, 24 June 2011 (UTC)


 * FYI, a third rail "only" carries 500-800 volts (which can still be dangerous); a power line, on the other hand, can carry anywhere between 11 kV (your typical local distribution line on wooden poles) and 1150 kV (the high-voltage transmission line between Irkutsk and Alma-Ata). See the difference? 67.169.177.176 (talk) 21:50, 24 June 2011 (UTC)


 * I guess they didn't have 500 kV, which might be enough to create sparks between the droplets. Sometimes I wonder how large the current is when rain flows over the insulators of a high-voltage line. Icek (talk) 07:32, 24 June 2011 (UTC)


 * Large enough that you can get a corona discharge (which is AFAIK what causes that annoying buzzing sound that power lines sometimes make). 67.169.177.176 (talk) 21:42, 24 June 2011 (UTC)


 * Shockingly, peeing onto an electric fence is not recommended. I wouuuld know this from having not seen the live wire that zapped me. --Modocc (talk) 15:07, 24 June 2011 (UTC)


 * WP:OR I've heard of a worker who was fatally electrocuted when he (unknowingly) pissed on a live electric cable which was carrying "only" 11 kV (and was insulated, as well). 67.169.177.176 (talk) 21:36, 24 June 2011 (UTC)


 * Mythbusters agree on that one, the test above was for the third rail where a person would be too far that urine was bound to break up. (This is referenced in the above article I believe because I read it a few weeks ago.) For an electric fence the person can be much closer. I do agree that applying a low voltage situation to the high voltage of power lines doesn't work Nil Einne (talk) 05:51, 25 June 2011 (UTC)


 * Um, don't they just switch off the electricity in those power lines before the workers climb up? &#x2013; b_jonas 13:37, 24 June 2011 (UTC)
 * It depends on the kind of work that is being done. For routine maintenance or inspection on very important wires, shutting them off is not necessarily an economical or desirable option (shutting off the electricity for an entire region, for example, can cause more danger to more people than it would to a properly trained operator). This is a pretty amazing video showing how inspections of high voltage transmission wires are done. As you can tell, they are very live — the operator is just kept away from anything that could ground them. He does not appear to have anything protective on (because he's not grounded). --Mr.98 (talk) 14:44, 24 June 2011 (UTC)
 * That hooded suit he's wearing is probably full of metal wires - it's a lighter version of the chain mail mentioned above. --Tango (talk) 22:52, 24 June 2011 (UTC)
 * Yeah, in the video, the guy says that the suit in the video is made out of 25% stainless steel thread. Red Act (talk) 02:46, 25 June 2011 (UTC)


 * Most electric utility workers you see working on poles next to the road are working on subtransmission lines of say 4kv to 34kv AC phase to phase. The transmission lines of 69kv, 138k and higher are a different kettle of fish. No practical amount of rubber protective gear would insulate a grounded worker from death when he touched an energized transmission line, so he works it deenergized or while isolated from ground, and the conductive suits come into play. If the transmission line worker were also touching something grounded, the conductive suit would not protect him from incineration. At the lower subtransmission and distribution voltages, insulation is practical and live line work is done commonly. The gear is beyond what an amateur could likely conjure up so do not attempt it. US utilities would typically require them while working on 12kv or 4 kv wires to wear a hardhat, approved safety glasses, fire retardant shirt and pants, "serviceable shoes" which have substantial soles and come high enough to provide ankle support (no sneakers or running shoes). No metal conductors under the protective gear. If they climb the wooden pole, they will use a climbing belt which goes around the pole and they would have "gaffs" attached to their boots which dig into the pole. They have to lean back for the belt and gaffs to hold, and they lean in too much, they will find themselves sliding down a splintery pole. If they are going to be near live high voltage wires they will wear thick rubber gloves tested to insulate to a higher voltage than the energized equipment in question (way thicker than dish washing rubber gloves), which have leather protective gloves outside them to protect from abrasion. They are likely to wear a harness for fall protection, with a rope which extends to break the fall in a shock absorbing way. The harness also allows them to be more easily lowered to the ground by rescuers if they are knocked unconscious. They are likely to additionally wear rubber sleeves which protect the arms. All this is heavy, cumbersome and hot, and there is a temptation to take short cuts, so there are commonly unannounced safety audits by supervisors. Mistakes and carelessness lead to death, severe burns, and amputations of burned limbs. A worker doing some switching operation at ground level might wear variations on the above equipment, less the climbing belt, gaffs, and harness, but adding an insulating cape and facemask, since a switching error could produce a huge fireball for a bit until fuses or breakers operated. Power voltages of 480 and up are good at sustaining an arc which  incinerates everything in the room, besides the electrocution hazard. Edison (talk) 15:58, 25 June 2011 (UTC)

This is an interesting problem. A person of length L stands on the ground, wearing perfectly insulating shoes. He is right underneath a powerline at a height of H above the ground. The powerline is at a voltage of V, the angular frequency is omega. Estimate the current through the person. Count Iblis (talk) 18:36, 25 June 2011 (UTC)
 * Negligible. It's only going to be significant if you get arcing, where the air is turned into plasma and becomes much more conductive. --Tango (talk) 18:42, 25 June 2011 (UTC)
 * Which brings up another question: Do linemen who work on high-voltage power lines (300 kV and up) really walk around with a halo around their heads? 67.169.177.176 (talk) 18:49, 25 June 2011 (UTC)

muscle cramp consequences?
From time to time I get muscle cramps, usually in a calf or hamstring, at which time my body basically tells my brain that I need to do whatever it takes to straighten that muscle and prevent it from contracting further. After pulling my toes towards my knee (calf cramp) or straightening my leg (hamstring cramp), the cramp passes (unwinds, kinda) and the muscle returns to normal function. I think most people here have experienced this process, certainly any athletes. What I'm curious about is what would happen if I did not stretch out the cramping muscle? if I just let it continue to seize up and contract? Does the cramp impulse eventually dissipate? can the muscle actually damage itself through a prolonged contraction? I've always wondered about this but have never been quite curious enough to put up with the pain and cognitive dissonance (why aren't you straightening that muscle? this is an emergency!) to experiment on myself... The Masked Booby (talk) 02:17, 24 June 2011 (UTC)


 * I can speak (WP:OR) for foot, calf and quad, ab- and adductor cramps. I was not able to get out of bed easily for about 10 days post surgery, during which time I had horrendous cramping. There is a peak point (very painful) in a cramp and it can hold there for what seems like forever, but is probably measured in minutes, and then it fades. You can't think about much else when it is happening, and I can now understand how cramps can cause swimmers to drown. I am not suggesting this will be everyone's experience. The article Cramp says nothing about possible damage from them. Bielle (talk) 02:32, 24 June 2011 (UTC)


 * In corroboration of Bielle, I can also offer some personal experience. For a period during my teens, I suffered occasional calf muscle cramps when sitting on wooden chairs in my (very crowded) school chapel during longer Sunday services. Since there was already very little space to move, and because drawing attention to myself was something to be avoided, I just had to leave my muscle contracted and grit my teeth until the cramp passed of its own accord after a few (2-4) minutes (incautious tensing of the muscle for 10 minutes or so after it had would sometimes cause it to return). No apparent muscle (or tooth) damage resulted. {The poster formerly known as 87.91.2301.95} 90.201.110.36 (talk) 17:29, 24 June 2011 (UTC)

Sugar water injection
On season 3 episode 12 of the espionage television series Burn Notice, a character uses a syringe to inject another character with sugar water in order to deceive that other character into believing that he had been injected with a deadly poison when in fact he had been injected with something harmless. Is it really true that injected sugar water is harmless? And why would the character use sugar water rather than just plain water? Was the sugar an unnecessary detail by the writers? —SeekingAnswers (reply) 14:53, 24 June 2011 (UTC)


 * Typically, doctors will use saline when giving fluids intravenously. One of the main reasons for this is that they want a solution which is isotonic with blood, so that the cells don't swell up from water absorption (see picture on that page). With saline, the osmotic pressure of the solution is regulated by salt, but osmotic pressure can also be regulated by any solute, including sugar. Why did the writers specify sugar instead of saline? I'm not sure, but my guess is that they were making a connection to the concept of a placebo, which are sometimes colloquially referred to as "sugar pills". -- 174.24.222.200 (talk) 15:46, 24 June 2011 (UTC)


 * Another couple of questions then: How does one go about determining how much salt or sugar is necessary for the solution to be isotonic with blood? And why would swollen cells be bad &mdash; that is, what kind of symptoms would present themselves? —SeekingAnswers (reply) 01:28, 25 June 2011 (UTC)


 * Initially, it would have to be determined experimentally, for example with an osmometer, or by observing the effect of solutions of various concentrations on red blood cells. However, since osmotic pressure is a colligative property, once you figure out the concentration needed for one solute, you can figure it out for pretty much any other. Typical IV saline is 9g/L, which is about 0.154 M NaCl, or 0.307 M solute molecules (0.154 M Na+ + 0.154 M Cl-). So you would need about a 0.3 M sugar solution. For a typical 10 mL syringe, this works out to about 1.05 g of sucrose (or 550 mg of glucose). A quick experiment with a kitchen scale shows this to be about 1/4 of a tsp of sucrose (probably about the amount of sugar in a small hard candy). - Regarding swollen cells, a temporary swelling of the cells isn't so much of a problem, (as it will likely reverse when the cells hit general circulation, and the hypotonic bolus is diluted out) but that if the solution is hypotonic enough, and the cells are bathed in it long enough, the cells may swell to the point at which the membranes rupture. This is called hemolysis, and if it happens to enough of the cells, can be fatal (although I doubt a ~10mL pure water bolus would cause enough damage to be fatal in most cases). -- 174.24.222.200 (talk) 17:56, 25 June 2011 (UTC)
 * Alternatively, IV bottles may also contain glucose. ~ AH1 (discuss!) 16:18, 24 June 2011 (UTC)


 * Note that the sugar solution given in hospitals is highly diluted (with water). Injecting a stronger concentration of sugar could be deadly. StuRat (talk) 17:19, 24 June 2011 (UTC)


 * An strongish isotonic balanced, glucose injection would cause a sugar rush. A subject so primed could very well believe this to be the symptoms of poisoning.  This sort of conviction  was observed by doctors in the Nazi death camps during their experiments. During the the 1991 Iraqi missile attack on Israel, a number of people suffocated in independent  incidents, thinking that carbon dioxide poisoning was confirmation of a gas attack and so dared not to take there gas masks off (they forgot to take the seals off the filtration canisters).   --Aspro (talk) 21:49, 24 June 2011 (UTC)


 * I'm not sure what you mean when you wrote "an strongish isotonic balanced." That doesn't seem to be proper English. Could you clarify? —SeekingAnswers (reply) 01:28, 25 June 2011 (UTC)


 * The sugar rush is unlikely to be true. I haven't looked over the article Hyperactivity. Imagine Reason (talk) 14:04, 25 June 2011 (UTC)


 * Also questioning the normal (nondiabetic) person perceiving a "sugar rush" from glucose in the bloodstream. If he eats candy or drinks a 32 ounce sugar soft drink, there will be heightened glucose in the bloodstream, leading the pancreas to release insulin, preventing the blood sugar from going very high. Consider the old glucose tolerance test, in which the blood sugar goes high after a big dose of glucose orally, but promptly comes back down in the normal person. No strange sensation in the gluconormal. Edison (talk) 15:32, 25 June 2011 (UTC)
 * 32 ounce, is that 2 pints? Can someone drink 2 pints of sugary drink? That is a huge dose, surely? Half a pint would be a more normal drink but still quite a hit of sugar. Or am I wrong about the quantity? Itsmejudith (talk) 21:37, 25 June 2011 (UTC)


 * It is a huge dose, but people really do drink it. Note that it's two American pints; if you're used to Imperial pints, those are bigger. --Trovatore (talk) 00:25, 26 June 2011 (UTC)


 * 7-Eleven has drinks up to a gallon in size, although that one is called the "Team Gulp", implying it would be shared. The "Double Gulp" is 64 ounces, though, and I bet some people drink that solo: 7-Eleven. StuRat (talk) 02:43, 27 June 2011 (UTC)

fish
Do fish sleep? — Preceding unsigned comment added by 69.27.150.44 (talk) 15:30, 24 June 2011 (UTC)


 * If I remember correctly, they do, but they swim while they do; that might just be sharks though. Sir William Matthew Flinders Petrie &#124; Say Shalom! 15:32, 24 June 2011 (UTC)


 * There is some information (but not a lot) at Sleep (non-human). Gandalf61 (talk) 15:41, 24 June 2011 (UTC)


 * Fish are incapable of closing their eyes, so they look awake when they sleep. Dolphins meanwhile sleep with one eye open. ~ AH1 (discuss!) 16:17, 24 June 2011 (UTC)


 * Yeah, but the guy asked about fishies, not about sea-going mammals. :p It is nice to note though (they're just like cats then). Sir William Matthew Flinders Petrie &#124; Say Shalom! 16:53, 24 June 2011 (UTC)
 * And yet, a sea-going mammal is more closely related to a bony fish than said fish is to the types of "fish" referenced in Flinders Petrie's reply. Yay Linnaean taxonomy! Buddy431 (talk) 04:26, 25 June 2011 (UTC)


 * There is a downloadable PDF at #14 "Sleep in fishes". Bus stop (talk) 17:01, 24 June 2011 (UTC)


 * This may or may not have bearing on the question (joke). According to our article, Luca Brasi (fictional character in Mario Puzo's novel The Godfather) "…sleeps with the fishes". Bus stop (talk) 17:18, 24 June 2011 (UTC)
 * In that case, the fish aren't necessarily sleeping. He's, er, sleeping. With fish around him. Grandiose (me, talk, contribs) 20:47, 24 June 2011 (UTC)
 * Precisely. He's "sleeping", and he's with the fishes. Or whatever the equivalent creatures are in the Hudson. David Feldman, author of a number of "Imponderables" books, titled one of them "Do Fish Sleep?" or some such. ←Baseball Bugs What's up, Doc? carrots→ 22:32, 24 June 2011 (UTC)