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#41 |
Illuminator
Join Date: Jun 2007
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It's amazing how many of these "paranormal" icons seem to merge together. There always seem to be theories about how they link together in some way. I'm sure someone has a very good explanation as to how Bigfoot killed JFK to help cover Roswell.-Mark Mekes This isn't rocket surgery.-Bill Nye |
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#42 |
Heretic Pharaoh
Join Date: Nov 2007
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#43 |
Illuminator
Join Date: Jun 2007
Posts: 3,785
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It's amazing how many of these "paranormal" icons seem to merge together. There always seem to be theories about how they link together in some way. I'm sure someone has a very good explanation as to how Bigfoot killed JFK to help cover Roswell.-Mark Mekes This isn't rocket surgery.-Bill Nye |
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#44 |
ETcorngods survivor
Moderator Join Date: Dec 2005
Posts: 23,097
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More like hundreds of thousands to millions of ohms.
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The one problem that can arise, though, is that you are getting into the "can not let go" range so other factors may come into play (difficultly breathing, injury from falls, etc.). It is a little far fetched, but not completely out of the questions. |
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#45 |
Heretic Pharaoh
Join Date: Nov 2007
Location: Pi-Broadford, Australia
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Cool. My next question is: If an AA battery has a capacity of 2850 mAh, and will produce 2850 mA for an hour, why won't it kill you with 2.8 Amps over 3 seconds or so, kinda sneaky like? ETA: Rhetorical only. Please don't waste too much time answering it, if any at all. ![]() |
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#46 |
Heretic Pharaoh
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#47 |
Illuminator
Join Date: Jun 2007
Posts: 3,785
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There is two accepted ranges. The range that you are citing is for macroshock. Macroshock is what most people traditional associate with electorcution. You grab a wire and you sizzle. The other form of electroctuion is microshock. That form of electrocution is commonly cited in the microamp range. It very specialized and I doubt most people who undergo electrical safety training know of it unless you work in a hospital. Mircoshock is when you have current directly across the heart. The only time when this is a problem is when you have catheters and other doodads providing a path of current directly to the heart. This difference is quite important and very exploitable in applications like pacemakers.
Technically I should know the answer to that question.
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__________________
It's amazing how many of these "paranormal" icons seem to merge together. There always seem to be theories about how they link together in some way. I'm sure someone has a very good explanation as to how Bigfoot killed JFK to help cover Roswell.-Mark Mekes This isn't rocket surgery.-Bill Nye |
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#48 |
ETcorngods survivor
Moderator Join Date: Dec 2005
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A proud member of the Simpson 15+7, named in the suit, Simpson v. Zwinge, et al., and founder of the ET Corn Gods Survivors Group. "He's the greatest mod that never was!" -- Monketey Ghost |
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#49 |
Heretic Pharaoh
Join Date: Nov 2007
Location: Pi-Broadford, Australia
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Apart from the Ohm's law bit of the thing, a dry battery simply can't carry out its internal chemical reaction fast enough to produce that sort of current. I know the fibrillation is a worry, but I always thought the grabbies was a DC only problem. Live and learn, I guess, and that's why we use the back of our hand, eh? I've had some of my worst beltings off DC. TVs are my nemesis and regularly throw me about the room. |
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#50 |
Illuminator
Join Date: Jun 2007
Posts: 3,785
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__________________
It's amazing how many of these "paranormal" icons seem to merge together. There always seem to be theories about how they link together in some way. I'm sure someone has a very good explanation as to how Bigfoot killed JFK to help cover Roswell.-Mark Mekes This isn't rocket surgery.-Bill Nye |
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#51 |
Heretic Pharaoh
Join Date: Nov 2007
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#52 |
ETcorngods survivor
Moderator Join Date: Dec 2005
Posts: 23,097
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It was my understanding that tetanus (locked muscles, can't let go, grabbies) was more of a problem with DC than with AC, but was somewhat compensated for by the tendency of DC to throw the victim clear of the conductor.
Other than that, though, volt for volt, AC was 3 or 4 times worse for ones continued existence than DC. |
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A proud member of the Simpson 15+7, named in the suit, Simpson v. Zwinge, et al., and founder of the ET Corn Gods Survivors Group. "He's the greatest mod that never was!" -- Monketey Ghost |
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#53 |
Illuminator
Join Date: Jun 2009
Posts: 4,501
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DC causes muscles to contract, and since it doesn't fluctuate, keeps the muscles contracted (grabbies).
AC's fluctuation is what may save you from the grabbies...but b/c of the frequency is more likely to interfere with normal heart fibrillation which is why AC requires few(er) amps to be deadly... |
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#54 |
Heretic Pharaoh
Join Date: Nov 2007
Location: Pi-Broadford, Australia
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Thanks guys. I've been a sparky all my life, but those last few posts have clarified stuff that I seem only to have ever half understood.
In any case, I take the same precautions with both flavours, and regard them both as potentially bitey. Kind of like an 'all guns are loaded' thing. |
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#55 |
Loggerheaded, earth-vexing fustilarian
Join Date: Sep 2006
Location: Usk, Wales
Posts: 26,557
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Great thread.
Started with a minor innocent static shock and ended with violent disagreement about various means of electrical death. This is what JREF is all about! Keep it up ![]() |
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#56 |
Graduate Poster
Join Date: Dec 2008
Posts: 1,856
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I've worked in labs with literally thousands of computers, all of them either desktop machines or rackmount machines, and I frequently would get shocked touching them, many times a day. I got to the point where I instinctively touched a machine with the back of my hand first (hurts less) to discharge any static that I had built up. Which brings me to the second point: your laptop is not building up static, you are.
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#57 |
Heretic Pharaoh
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#58 |
Heretic Pharaoh
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#59 |
Illuminator
Join Date: Jun 2009
Posts: 4,501
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Agreed.
And I'll admit that my previous comment that started this side-discussion was a bit excessive. What we do is we look at it like this: We have a current (8A), we know that the voltage is 19V...putting those into ohms law (to solve for the resistance we'd get those values at: R = V/I ) we see R = 19/8. If your skin was ever to get to around 2ohms, you'd see the full dose of 9A. Solving for the current flow of 19V at 1000ohms (wet skin), we use I = V/R > I = 19/1000 > I = 19mA. Not near enough for a lethal dose, so on that point I concede. My power supply would not be able to kill a human (unless you used it to bludgeon someone with or the voltage regulator goes bad). However, I maintain that voltage isn't the killer. It's the current flow (amps) through the heart causing fibrillation (heart attack). |
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#61 |
ETcorngods survivor
Moderator Join Date: Dec 2005
Posts: 23,097
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I'm not so sure. It seems like most of the online references for either tetany or tetanus take a solid medical perspective (where the former is calcium related and the latter, bacterial) for muscle contraction conditions. Wikipedia seems a bit broader than most for tetany by admitting "or other conditions". The "other conditions" certainly could be electrical shock.
The couple of dictionaries I tried tended towards the opposite. Tetany was solidly a medical condition related to abnormal calcium metabolism while tetanus could be more than just "lock jaw." Bottom line: I'm confused and will admit it. ![]() |
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#62 |
Master Poster
Join Date: Aug 2007
Posts: 2,060
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Too many to choose from. I'll let you select them given that A/ anyone should know a laptop is not only not grounded, but is explicitly isolated from the power ground B/ a power ground isn't needed for a static discharge.
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#63 |
Heretic Pharaoh
Join Date: Nov 2007
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Why should 'anyone' know this? Do you include people who have never seen a computer of any description? 6-month-old babies? The lack of specific examples makes it seem that you might not have any. If you do, then at this stage, you'd better make them really, really good ones. |
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#64 |
Illuminator
Join Date: Jun 2007
Posts: 3,785
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Freaking hell. I go into detail about how that statistic is wrong and you still botch it up. Cut skin has a resistance of zero ohm's!!!!!!!!!! And its also a stupid metric. Given that my grandpa's pacemaker battery is capable of stopping my grandpa's heart and remains operational for about two years and is only the size of a hearing aide battery something is wrong with your logic. My grandpa would be dead if it was solely current that kills.
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__________________
It's amazing how many of these "paranormal" icons seem to merge together. There always seem to be theories about how they link together in some way. I'm sure someone has a very good explanation as to how Bigfoot killed JFK to help cover Roswell.-Mark Mekes This isn't rocket surgery.-Bill Nye |
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#65 |
Heretic Pharaoh
Join Date: Nov 2007
Location: Pi-Broadford, Australia
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Oh rly? I rather think the consensus is that you can't have current without voltage and saying that one or the other will kill you is a nonsense statement. That's why people come here and ask questions. Works well, doesn't it? |
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#66 |
Illuminator
Join Date: Aug 2008
Posts: 4,024
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Personally, I go with the CDC. I linked Wiki because it is generally more understandable, and in this case I knew it to be pretty correct (even if it didn't go into great detail).
Tetanus is the name of a disease which is caused by bacteria (C. tetani, aka "tetanus bacillus"), for which most people in developed countries are vaccinated against regularly. http://wwwnc.cdc.gov/travel/yellowbo...2/tetanus.aspx Tetany is a medical sign in which the patient's muscles contract involuntarily. The most common cause is a calcium imbalance/lack. There are other causes, but those are either much more rare, or only occur in non-humans (cows, for example, have their own version of tetany). I'd link a definition from the CDC, except the CDC assumes readers already know the definition, so don't provide one. If you search the CDC site for it though, you'll get a big long list of results where it is a symptom of a larger disease/condition. You cannot vaccinate against tetany. Neither one is technically applicable to the situation, as you're talking about a muscle spasm caused by an electric shock and not a disease or a symptom of a disease. But tetany is much closer to describing the results of an electric shock than tetanus is. |
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#67 |
hairy farting brute
Join Date: Mar 2008
Posts: 970
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Milliampere hours are not a measurement of how much current a battery can deliver, they’re a measurement of how much energy it stores (which is not relevant to this discussion). For example, in theory, a perfect 2000 mAh battery could deliver 8000 mA for fifteen minutes (or, say, 1000mA for two hours) before being drained.
The current a real battery can deliver is limited by other factors, which in circuit theory is represented by “internal resistance”. For the sake of experiment a few years ago, I momentarily shorted a 2500 mAh AA cell through my multimeter. It read about 1800 mA. |
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#68 |
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#69 |
Muse
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It makes sense, if you don't think about it. - T-Mobile ad You're innocent when you dream. - Tom Waits Religion was invented when the first con man met the first fool. - Samuel Clemens |
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#70 |
ETcorngods survivor
Moderator Join Date: Dec 2005
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A proud member of the Simpson 15+7, named in the suit, Simpson v. Zwinge, et al., and founder of the ET Corn Gods Survivors Group. "He's the greatest mod that never was!" -- Monketey Ghost |
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#71 |
Heretic Pharaoh
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#72 |
ETcorngods survivor
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A proud member of the Simpson 15+7, named in the suit, Simpson v. Zwinge, et al., and founder of the ET Corn Gods Survivors Group. "He's the greatest mod that never was!" -- Monketey Ghost |
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#73 |
New Blood
Join Date: May 2009
Posts: 6
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I just measured my laptop power supply (which does have a "earth" pin), and the output voltage 0V is actually connected to the mains earth. That means the laptop's USB port etc are also connected to mains earth, just as for desktop computers.
This is better than my previous laptop, which didn't have an earth pin, and which would sometimes give me a very small "tingle" when I touched the output connector when standing on tiles. This was due to capacitive coupling in the power supply injecting a small 50Hz voltage on the output connector (ie, it was NOT due to static electricity). |
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#74 |
Heretic Pharaoh
Join Date: Nov 2007
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Yup, that sounds about right. I've got a few bricks and other power supplies that are earthed through the mains plug. Especially older transformer types. You've reminded me of something else too. I wonder how many non-sparky people realise that Earth isn't as 'low' as a voltage can get, and that in fact a lot of equipment has a negative rail that's 'below' Earth. |
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#75 |
Heretic Pharaoh
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#76 |
ETcorngods survivor
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A proud member of the Simpson 15+7, named in the suit, Simpson v. Zwinge, et al., and founder of the ET Corn Gods Survivors Group. "He's the greatest mod that never was!" -- Monketey Ghost |
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#77 |
Heretic Pharaoh
Join Date: Nov 2007
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I think we might be risking modulation here.
In seriousness, I can't think of anything else to add that might assist the OP, but I'm happy to clarify anything I might have said. A bit of general electrical knowledge is a good thing for everyone to have, I reckon. 'tis dangerous stuff, as much as I love it. |
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#78 |
Illuminator
Join Date: Jun 2007
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Not when BobTheDonkey keeps on giving out information that can get people killed.
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It's amazing how many of these "paranormal" icons seem to merge together. There always seem to be theories about how they link together in some way. I'm sure someone has a very good explanation as to how Bigfoot killed JFK to help cover Roswell.-Mark Mekes This isn't rocket surgery.-Bill Nye |
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#79 |
0.25 short of being half-witted
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"AND ZEPPELINS!!! We haven't even begun to talk about Zeppelins yet! Marauding inflatable Teutonic johnsons waggling their way across the sky! Indecent and flammable all at once." |
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#80 |
Heretic Pharaoh
Join Date: Nov 2007
Location: Pi-Broadford, Australia
Posts: 29,685
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It seems that JREF has cornered the market on electricians-who-wish-they-were-comedians.
I wonder watt that's all about. |
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