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| what's the current of a static shock? |
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| Zero999:
--- Quote from: bsfeechannel on November 20, 2020, 10:56:42 am --- --- Quote from: amyk on November 20, 2020, 04:25:41 am ---The lowest time on that graph is 10ms - a static shock (ESD event) is in the us/ns --- End quote --- It is also for AC current, but it seems to imply that above a certain current intensity, no matter how short the shock is, it can potentially cause some irreversible effect. --- End quote --- That chart is completely irrelevant to a static shock, which is several orders of magnitude shorter. |
| bsfeechannel:
--- Quote from: Zero999 on November 21, 2020, 11:07:29 am ---That chart is completely irrelevant to a static shock, which is several orders of magnitude shorter. --- End quote --- Maybe. But do you believe that if you have a current of arbitrary intensity running through your body, as long as it is as short as, say, 10μs, it will do you no harm? |
| T3sl4co1l:
Of course not. A strong enough current will cause spot heating, or even vaporization. The effect is used to detonate high explosives (exploding bridgewire, slapper). Granted, it's easier to generate that kind of power into metals using capacitors, than it is into much higher-resistance flesh. But a high enough voltage, on a correspondingly smaller capacitor, ought to do it. (Be careful around your Marx generator experiments, people?) Amazingly enough, people have survived direct lightning strikes. That's the biggest possible shock, and it's literally electrostatic in origin. Offhand I don't know the chances of survival, or how much internal damage is usually sustained. Certainly, one does not escape with no physical marks at all; the skin burn patterns are... incredible. :o It seems likely that ESD causes such damage, simply in a very thin area; maybe this damages very few cells, or perhaps it even slips by living cells, burning just intercellular matrix, easily repaired in either case, and not enough damage to cause pain or physical problems. RF burns are notorious for a similar effect but sustained over a long enough period that a plug of flesh is literally burned out; which is supposed to hurt quite a lot, I forget if immediately or later on as toxins diffuse into surrounding healthy tissue... Tim |
| DrG:
So, instead of doing "work", I spent a few hours looking into the topic with the specific goal of seeing what kind of laboratory studies were out there...and there are many. This review https://ehjournal.biomedcentral.com/articles/10.1186/s12940-017-0248-y was pretty interesting, including the table of studies with humans https://ehjournal.biomedcentral.com/articles/10.1186/s12940-017-0248-y/tables/1 Of course, along the way, I came across the ignition liability (yes, a different issue)...like this case report https://www.ejmi.org/pdf/Facial%20burn%20due%20to%20static%20electricity%20induced%20fire%20%20A%20rare%20clinical%20entity%20Case%20Report-02886.pdf and this one, that seems to suggest a liability for ignition of hand sanitizer! https://pubmed.ncbi.nlm.nih.gov/29322859/ Alas, they have thwarted all of my usual methods for quickly getting the actual article, so all I can see is the abstract. Remember a while ago when the "cell phones cause fires at fuel pumps" was a thing, debunked to static electricity, but how does one decide the actual odds of a cell phone (not static electricity) has a 1 in 10 billion chance (assuming normal uses) of causing a fire at a fuel pump? https://www.ctvnews.ca/canada/one-in-10-billion-chance-cell-phone-could-ignite-vapours-at-gas-station-report-1.4332547 |
| Zero999:
Of course static electricity isn't completely harmless. Not only is there the potential for ignition, but involuntary movements could result in injuries. I suppose one could argue that the shock itself will cause an injury, but it's very mild and will quickly repair itself. By the way, has anyone zapped insects with a piezo BBQ ignition before? That's one of the first things I did, when I got hold of one, as a child, after zapping myself and my siblings of course! Sometimes it would just stun the insect for awhile, but more often it one shock was fatal. Obviously it takes much less energy to harm a tiny insect, than a human. |
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