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Your resistance is most entertaining, meatbag.
August 3, 2013 4:28 PM   Subscribe


 
Ok, but I'm still gonna kill the main breaker just to install a Nest thermostat.
posted by planetesimal at 4:32 PM on August 3, 2013


I'm a little ambivalent about the electric shock one.

On the one hand it is funny, informative and well-written.

On the other hand his bragging about how many shocks he's taken through the chest makes him sound like an irresponsible jackass whose irresponsibility will eventually catch-up with him.

Also, no mention of the "one-hand-in-pocket" safety rule for people who aren't into cheating death.

IAAEE (I am an electrical engineer).
posted by ZenMasterThis at 4:46 PM on August 3, 2013 [14 favorites]


Also, no mention of the "one-hand-in-pocket" rule.

I think that was deliberate on his part, to focus on what exactly happens when there's an actual shock (i.e., a completed circuit), not on prevention. Although this does let me link this totally delightful video, which mentions the pocket-trick.
posted by kagredon at 4:53 PM on August 3, 2013 [1 favorite]


The electric shock one is very misleading. I don't care how many volts you got shocked by. It's the amps that will kill you. I've been hit by thousands of volts when I stupidly touched a car spark plug lead while grounded. It was like being hit by a cricket bat but it wasn't going to kill me. I've also taken 220v across my hand with plenty of amps and that hurt like hell but it wasn't going to kill me. But 100v will kill you very easily -- a classic situation being an wrongly wired guitar amp and a properly earthed vocal mic, which will stop your heart dead right there and then.
posted by unSane at 4:56 PM on August 3, 2013 [1 favorite]


Did you read the whole thing? He addresses why he's talking in terms of voltage instead of amps.
posted by kagredon at 5:13 PM on August 3, 2013 [1 favorite]


The electric shock one is very misleading. I don't care how many volts you got shocked by. It's the amps that will kill you.

Yes, but you do realize that the amperage is merely the end result of "how much voltage vs. resistance" you're dealing with, right?

Since "lethal amperage" is a known fixed point (i.e. 100-200 mA), and we can kinda guess our skin's resistance based on how wet it is, etc., the only variable left is: "how many volts will it take to kill me?"
posted by ShutterBun at 5:16 PM on August 3, 2013 [3 favorites]


Fun trick I heard somewhere: if you must touch bare wire, for whatever reason, use the back of your hand. If your hand muscles contract from shock, at least you're not likely to grab on to and hold the lead.
posted by Blazecock Pileon at 5:17 PM on August 3, 2013 [5 favorites]


Meatbag?

Retraction: Did I say that out loud? I apologize, master. While you are a meatbag, I suppose I should not call you as such.
posted by Palquito at 5:30 PM on August 3, 2013 [8 favorites]


There's also the "disturbing amperage" problem for animals. Since they don't usually wear shoes and are often wet, cows have an impedance of around 300 Ω; they also have a longer span between their hoofs than we do between our feet. Result: a vulnerability to stray voltage. My cousin got that problem on his dairy farm; it took him six months to finally get it fixed for good.
posted by Monday, stony Monday at 5:31 PM on August 3, 2013 [5 favorites]


Fun trick I heard somewhere: if you must touch bare wire, for whatever reason, use the back of your hand.

i can confirm that - my grandfather said the same thing, and he was a professional electrician
posted by pyramid termite at 5:48 PM on August 3, 2013


Another electrical safety tip: never plug in a live cable. In other words, the power end of the cable should be connected last. This was passed down as family wisdom from my Dad, who discovered first hand why that rule exists.
posted by ceribus peribus at 5:59 PM on August 3, 2013 [1 favorite]


ceribus peribus: "Another electrical safety tip: never plug in a live cable. In other words, the power end of the cable should be connected last. This was passed down as family wisdom from my Dad, who discovered first hand why that rule exists."

10 or so years ago the company I was working for leased some colocation space from a local CLEC, which generally means that the overwhelming majority of the equipment in the place was telco-related, which also means that all of it ran on DC.

Now, you can buy servers with DC power options for such places, but we hadn't done that and weren't really in a position to go replacing all of it. The colo was so desparate for tenants that the rent was almost nothing and they threw in a pair of gigantic inverters so that we could convert their DC back to AC and thus power all of our gear.

These things were huge. About as tall as refrigerators but not quite as deep. The electrician came in and was wiring them all up and then we (which is to say he) hit a bit of a problem. A classic start-up state problem. To wit:

The documentation covered power-cycling the units, but not turning them on from zero. Turning them on from scratch was not the same as turning them on after having been off. After a bit of head-scratching, he realized that he was going to have to connect them...live. Like, to live power. This, he assured us, was no big deal, but we all stepped outside of the cage while he worked. He had just been regaling us with the usual assortment of electrician's horror stories and none of us were interested in standing in a room-sized bug-zapper.

It went off without a hitch, of course, but I still get the willies thinking about it which is why I am not an electrician, outside of replacing an outlet or light switch.
posted by jquinby at 7:06 PM on August 3, 2013 [5 favorites]


unSane: "The electric shock one is very misleading. I don't care how many volts you got shocked by. It's the amps that will kill you."

It's not quite that cut-and-dried though…

Assuming the same body resistance, the current @ 220/240v is double that of 110v. But in 220/240v western countries, electrical fatalities are consistently less than half of those in 110v countries. The same goes for countries with mixed 110v / 240v systems (e.g. bits of central & south America, the Middle East, & North Africa). Why?
  • The current @ 110v tends to paralyse muscles, causing the victim to not be able to move or let go. The current @ 220/240v causes muscles to contract, and the victim is more likely to pull / fall away from contact.
  • With a shock across the chest, the current @ 110v generally sends the heart into fibrillation, and it struggles to return to a normal rhythm. The current @ 220/240v tends to stop the heart completely - from which it's much more likely to restart & return to a normal rhythm unaided.
posted by Pinback at 7:07 PM on August 3, 2013 [14 favorites]


Also, no mention of the "one-hand-in-pocket" safety rule for people who aren't into cheating death.

My Dad, an EE at a U.S. Navy submarine R&D lab with the well-earned nickname "Sparky", taught it to me thus:
"One hand for the ship, one hand for yourself. Keep it in your pocket."
I never had the guts to do it bare-handed, so I went the extra mile. A loooong plastic-handled screwdriver saved my ass when wiring an outlet for a dryer - tapped it once on the exposed leads, one hand in my pocket. Giant shower of sparks, melted screwdriver tip, and a bitter resentment for whoever labeled my breaker box.
posted by Slap*Happy at 7:26 PM on August 3, 2013 [3 favorites]


This does raise a good question of how exactly are you supposed to connect equipment to live bus bars, when you obviously can't de-energize them in a CO?
posted by kiltedtaco at 8:00 PM on August 3, 2013 [1 favorite]


I'm more curious about the Depeche Mode button on my microwave.
posted by symbioid at 8:09 PM on August 3, 2013 [2 favorites]


It's for your own personal Jesus.
posted by Slap*Happy at 8:26 PM on August 3, 2013 [10 favorites]


now in pepperoni flavor
posted by kagredon at 8:42 PM on August 3, 2013


The current @ 110v tends to paralyse muscles, causing the victim to not be able to move or let go. The current @ 220/240v causes muscles to contract, and the victim is more likely to pull / fall away from contact.
With a shock across the chest, the current @ 110v generally sends the heart into fibrillation, and it struggles to return to a normal rhythm. The current @ 220/240v tends to stop the heart completely - from which it's much more likely to restart & return to a normal rhythm unaided.


Do you have a source for that? I thought it mostly came down to better standard enforcement in Western Europe.
posted by Monday, stony Monday at 8:42 PM on August 3, 2013


Never, ever roll up the extension cord from the "plug in" end. Unless you are absolutely, totally, completely, 100% sure that the cord is unplugged.

But if you're sure it's unplugged, that means you -- you, personally, and not anybody else, damn sure not the apprentice -- you looked at it, and you saw with your very own eyes that it's unplugged, and if you saw that, if you were right there and saw that, then why didn't you start from that end and roll the cord up, instead of walking 100' and starting from the dummy end?

Rolling up a cord, you're going to have it in your hands, you're going to be actually rolling it around your arm, and when you hit a bare spot -- not if, when -- when you hit a bare spot in a cord, and you've got it wrapped around your arm, you are now officially in deep shit. Because you're going to grab onto that cord, and it's wrapped around your arm.

You say your cord doesn't have any bare spots. Hey, it's a brand new cord! But you weren't there, you were on a coffee break when the A/C guy ran it over with his scaffold, and the cord was on a piece of sharp metal, and got cut, not enough to sever it, just enough to gouge it, and expose you to the juice that afternoon, at the end of the day, when you're tired, and just this once you're going to roll it up from the dummy end.
posted by dancestoblue at 8:48 PM on August 3, 2013 [14 favorites]


This does raise a good question of how exactly are you supposed to connect equipment to live bus bars, when you obviously can't de-energize them in a CO?

My practice has always been to place blankets of proper dielectric strength over all grounded portions of the equipment, as well as any opposing phases. get myself properly gloved up, then drill,tap and connect one phase at a time. the necessary order is ground, neutral, and then the phases. Of course the order is reversed when disconnecting.

Don't get in a hurry, and pause to get rid of perspiration on a regular basis. Also, never do this alone.
posted by scottymac at 8:51 PM on August 3, 2013 [3 favorites]


Do you have a source for that? I thought it mostly came down to better standard enforcement in Western Europe.

Easily verifiable, really. The "lethal" range of amperes is around 100-200mA, due to it confusing the heart muscles, etc. But above that, the heart does what they (apparently) call "clamping", where it simply stops altogether, then (usually) restarts normally. I'm guessing this is the same principles used by defibrillators, which do not "shock your heart back to life" but rather they stop it, initiating sort of a "soft reset" on the whole thing.
posted by ShutterBun at 8:55 PM on August 3, 2013 [3 favorites]


you're going to be actually rolling it around your arm,

Don't wrap extension cords around your arm, even when unplugged. It is hard on the extension cord and makes a tangled mess when you go to use the cord again. Hold it in one hand and use the overhand-then-underhand loop method. This is too hard for me to explain in words, so find a roadie to show you how.
posted by tommyD at 8:56 PM on August 3, 2013 [5 favorites]


"...and you've wrapped it around your arm,"

...and right there is your second mistake.
posted by Floydd at 8:59 PM on August 3, 2013 [1 favorite]


Or what tommyD said.
posted by Floydd at 9:01 PM on August 3, 2013


Info on fatal currents.
posted by ShutterBun at 9:02 PM on August 3, 2013 [1 favorite]


During my luckily short banking "career", I had the fortune to work at the local power companies' credit union. I was there like six or seven months, and I saw like fifteen or twenty guys who were badly burnt from working power lines, and ever since then, I've had an overpowering respect for people who choose to work with that deadly magic smoke.

How hard is it to die of an Electric Shock?

If it's in the right spot, a tiny bit of electricity can stop your heart. Good luck with that.
posted by Sphinx at 9:10 PM on August 3, 2013


Hold it in one hand and use the overhand-then-underhand loop method.

I found a you tube video.
posted by tommyD at 9:10 PM on August 3, 2013 [11 favorites]


Gloves. I forgot that gloves exist. That makes a lot more sense than anything I was thinking.
posted by kiltedtaco at 9:11 PM on August 3, 2013 [1 favorite]


I found a you tube video.

Thank you very much. Now I have something else to be immediately obsessive about.
posted by de at 9:26 PM on August 3, 2013 [1 favorite]


Oak Brook shopping center, suburban Chicago, cold, rainy autumn day, 1981. A Kodak photo shop moved out of the shopping center, we were remodeling it for whoever was moving in. Dress shop? No telling. The mists of time, and all that. Anyways, that photo shop had had lots of big pieces of equipment, run by big juice.

The laborers -- a bunch of Polish immigrants, working for Terry, who was a first generation American Pole and spoke Polish and hired them on as unskilled labor (we used to call them "Terry and The Pirates") -- the laborers tore out all the walls -- the drywall, the metal studs, whatever else needed to go. For whatever reason, they'd not torn out this one section of conduit, leading to a big electrical box; they'd taken the finish trim off, they removed the plug receptacle, they shoved all the wires back into the electrical box. No tape on them. No caps. Bare wires.

Surely, surely the laborers would never have messed with it if it was not cut off, if there was no juice to it. Surely, the superintendent on the job would have taken care of that, first off, before the demo, before anything -- I mean, come on, that's his job. Surely, Terry would have made sure that the juice to that thing was cut before he let his laborers mess with it. It wasn't even a question.

Clearly, I wasn't awake. I wasn't alert. Which was a mistake.

I was removing the box from the conduit, I was sortof scootched down, knees bent a little and bending over. I loosened the screw that held the box onto the conduit, and began twisting the box, to pull it over the wires.

It hit me like a truck. I've got one hand on the conduit, holding it while the other hand is twisting off the box. My body convulsed, slammed me backwards, into a sawhorse and a bunch of other shit, knocked it all down and I'm right in it all. The box came off as I slammed back, maybe it wouldn't have let me go had not the box been free, had not the screw been totally loosed, I don't know. I'd always heard that in some ways you want to get hit by more juice than less, because it'll blow you back from it, from your convulsing. But I don't know.

I was fuct for the rest of that day. Made me cry, not right away but not too long after, I was sitting with the other carpenter, Larry, we're talking, it's pretty heavy, I just started crying. I was just totally jazzed, wacked, smacked.

I can't recommend this to anyone.

And that's my Kodak photo shop story.
posted by dancestoblue at 9:28 PM on August 3, 2013 [12 favorites]


Don't wrap extension cords around your arm, even when unplugged. It is hard on the extension cord and makes a tangled mess when you go to use the cord again. Hold it in one hand and use the overhand-then-underhand loop method. This is too hard for me to explain in words, so find a roadie to show you how.

There's nothing wrong with arm wrapping if you use the right technique. The cord must be laid out flat to prevent twist and if you have arm wrapped enough times to gauge the size, you can loop the last 10 inches and plug the cord into itself. The key here is to avoid twisting the cord, but of course, the best way is to use a spool that makes it easy to lay and retrieve the cord.
posted by crushedhope at 9:50 PM on August 3, 2013


you're going to be actually rolling it around your arm,

Don't wrap extension cords around your arm, even when unplugged. It is hard on the extension cord and makes a tangled mess when you go to use the cord again. Hold it in one hand and use the overhand-then-underhand loop method. This is too hard for me to explain in words, so find a roadie to show you how.

posted by tommyD at 10:56 PM on August 3

Yeah I know, right? It's super-cool to roll cords that way, they don't get all twisty, they are (if you know how to do it) they are super easy to roll and to get unrolled, it's just very cool.

But I was in the trades for decades and still hang with blue-collar guys and almost no one does it. I surely don't. And guys sometimes want to choke other guys who roll up the cords that way, because it's a total PITA to unroll if you don't know the trick.

I don't roll cords so tight as to separate the or get them all bindy, if bindy is a word, and even if it isn't. And a real good cord has enough "firm" to it that you (I) don't need or want to roll it around your (my) arm, it'll easy loop into like 30" circles; most of the cords that I still have left are quality and roll that way.

But some cords just fall easy into winding around your (my) arm and don't get twisty and blah blah blah, I've got one for sure, maybe a couple. If I have a cord that gets twisty I'll give it to you, I'd give it to the apprentice if I was still on the jobsites.

(Plz note: Though I am in the majority, I am wrong here -- I confess it. But I'm still pretty sure that I;m not gonna learn the way your friend taught you, not unless you buy me a hat or something. Thank you.)
posted by dancestoblue at 10:02 PM on August 3, 2013


I am learning so many terrifying things from this thread.
posted by figurant at 10:15 PM on August 3, 2013 [1 favorite]


Fun trick I heard somewhere: if you must touch bare wire, for whatever reason, use the back of your hand. If your hand muscles contract from shock, at least you're not likely to grab on to and hold the lead.

I met a licensed electrician at a theater who told me this.

When I returned to the theater a couple of years later the same electrician had one fully-functioning hand. The other had severe and permanent damage from touching the wrong bare wire with the back of his hand.

This is not a trick guaranteed to work 100% of the time.
posted by soundguy99 at 10:17 PM on August 3, 2013 [5 favorites]


... I'm still pretty sure that I;m not gonna learn the way your friend taught you ...

Knitters have a distinct jump on the learning curve. I simple chanted "pearl one, knit one" and am now working on speed and pedantic loop size — 'tension', you might say. I've never been so happy with my extension cords. Unpicking unravelling is a breeze.
posted by de at 10:37 PM on August 3, 2013 [2 favorites]


why didn't you start from that end and roll the cord up, instead of walking 100' and starting from the dummy end?

Because at the next gig when you use the cord again you want whatever excess cable you have coiled up near whatever you're plugging into the female end so when someone goes, "Hey can you move that light 3 feet to stage left?" you can say, "Sure." and move the light without having to tug on umpty feet of cable buried under a bunch of other cables.

Also you don't end up with a giant friggin' rat's nest of coils of cables piled up around your power distro.

So you start from the male end, plug into the distro, then walk it out to its' destination, unwinding as you go. Reverse the process when packing up.

Different trade than dancestoblue, obviously. But yes, if I see someone wrapping a cable around their arm I will roll my eyes. If I see you wrapping one of MY cables around your arm I will yell at you and make you drop it. Although there's an "all overhand" version of wrapping cables that's usually fine for lengths under 50'.
posted by soundguy99 at 10:43 PM on August 3, 2013 [1 favorite]


Purl?

Disclosure: my father was a high voltage e/engineer. As a pre-schooler I was ruthlessly threaded into roof cavities and under-house gaps to further thread cable down or up wall cavities. He's died without my ever knowing if he knew this overhand-underhand loop method.

It will plague me the rest of my days.
posted by de at 10:53 PM on August 3, 2013


No-contact AC voltage detectors are a miracle.
posted by miyabo at 11:06 PM on August 3, 2013 [2 favorites]


Hold it in one hand and use the overhand-then-underhand loop method. This is too hard for me to explain in words, so find a roadie to show you how.

Actually, that roadie/stagehand will show you that some cable wants to be over/undered, while others just want to be spun and coiled the regular way, bringing one hand to the other while slightly rolling the fingers. Power cable tends to want to be coiled in this manner, while most audio and data cable wants to be coiled over/under. Cat-5 cable should be cut into 2 ft lengths and scattered everywhere in the drop ceiling.

As for power horror stories, I was once working in a marina on a 50amp outlet for shore power. The breaker box was mislabelled and I cut a cable I thought was safe. The resultant shock blew the tool out of my hand and into the water 20 feet away, as my boss laughed his ass off at the box. I haven't felt too friendly towards him since.
posted by nevercalm at 11:33 PM on August 3, 2013 [1 favorite]


The most juice I ever took was 50 amps of 220v. I was kneeling on a concrete floor when I had the wise idea to jiggle a fuse, & accidentally replaced it with my index finger & thumb. Threw me back on my ass HARD. Nearly knocked myself out hitting the floor with the back of my head, but I was okay after laying down on the couch in the office for about an hour. The thing I noticed most was that I was real, real calm the rest of the day. Sort of gave me a direct understanding of the effect of electro-shock therapy.

10-15 amps of 110 from a household wall plug? Pah. Mildly unpleasant. An ungrounded Sure sm 58 with the metal dust guard to a wet lip is a good bit worse, but usually just a rude surprise, though a few musicians have died on stage from bad wiring.
posted by Devils Rancher at 11:46 PM on August 3, 2013 [2 favorites]


If we are telling tales about getting shocked, I'll pitch in mine. I was an apprentice, July of '79 or so . Working on final lighting touches in a recently opened Sears store. From a position on the very top of a 12 foot 3 legged ladder, I removed a defective 277 volt ballast from a fluorescent light fixture without properly making double sure all power to it was off. It wasn't. I flew off the top of the ladder and fell into a pyramid display of the kind of cardboard sided motor oil cans that were common then. I was told by my co-workers the following day that it had been a splendid, if messy show.
posted by scottymac at 12:12 AM on August 4, 2013


The thing I noticed most was that I was real, real calm the rest of the day. Sort of gave me a direct understanding of the effect of electro-shock therapy.

That's interesting. The times I've been shocked, I always felt jittery and uneasy. Not unlike being strung out on caffeine. I wonder if there is a cult of loonies out there that shock themselves for self-medicating reasons?

My stupidest shock was thus: I was working the front counter at McDonalds. This was the time when they had free coffee refills available right at the counter. There was a warmer and some metal coffee pots. (Not glass, so they wouldn't break.) A customer informs me that he thinks there is a short in the warmer. Without thinking, I touch the coffee pot. I got a nice wham or foomp kind of noise, and my hearing turned off, and then rebooted slowly. I think the poor customer almost had a heart attack. I said "wow, you're right", unplugged the warmer and politely excused myself.

But I'll take that any day over getting shocked by a spark plug lead. Holy hell, that *hurts*.
posted by gjc at 3:09 AM on August 4, 2013 [1 favorite]


Oh yeah, I've pulled the "wiggle the spark plug wire" trick-- once. Felt like my whole arm had been hit with an arm- sized hammer.
posted by Devils Rancher at 3:16 AM on August 4, 2013 [2 favorites]


Also, no mention of the "one-hand-in-pocket" safety rule for people who aren't into cheating death.

This vital maneuver, which involves making a peace sign with your other hand, has helped an untold number of people realize what it all comes down to.
posted by threeants at 3:34 AM on August 4, 2013 [2 favorites]


Devils Rancher, you didn't take 50A at 220V. Sure you contacted a circuit capable of supplying that but you passed no more current than if you had contacted a 5A or a 4000A circuit. The voltage is a fixed quantity as is your bodies' resistance, ohm's law works out the rest without regard to what capacity circuit you are hooked up to.
posted by deadwax at 3:58 AM on August 4, 2013 [1 favorite]


So yesterday I had my bench power supply and electronics gear, breadboards, Arduino out and my broken old (awesome) Neverlate alarm clock as well as a new shitty RCA iPhone dock/alarm clock disembolwed on the dining table. The transformer in the Neverlate was on the fritz. Inside the alarm clock is some mostly analog circuitry for the AM/FM radios and amp and the alarm/display/buttons are digital and just work off 5-9VDC. Only the radio and amp needed most of what the transformer was doing. It was an easy process to yank out the broken transformer, use an external power supply and just give up on having a radio, and then figure out what to do with the cavity inside with the transformer and radio bits removed, to get the buzzer signal amplified so it can wake me up again. I was in the process of rigging components from the RCA to do this and also give it a nice little upgrade of charging/playing music from my iPhone with a lightning connector. Was doing some tests with both of them powered and also the messed up buzzing transformer plugged in for no good reason. Huge tangle of wires on the table and easily a few places I could touch that'd give me a little zap, most of them current-limited by my power supply but not everything.

I was a little bleary eyed after being at it all day and strung out with a little flaw in my frankenclock circuit to send button press pulses to the RCA board, and I took a break and went to the bathroom to shower and shave.

I rinsed out the plugged-in-to-AC rechargeable shaver that was clogged with hair in the sink, getting it and my hands nice and wet. I quickly shocked my right hand while holding it. Picked it back up before I knew why I dropped it and it got me again. Hurt just a little, tingled the rest of the day. I think there's a meaningful lesson here, but it's lost on me. At least don't use plugged-in electronics under running water.

UL should mandate that failure modes deliver current with characteristics similar to that of a Taser for fucking idiots like myself, because somewhere deep inside every time I get shocked and it's not a big deal I'm just getting braver.
posted by floam at 4:01 AM on August 4, 2013


Isn't the high voltage almost no amps how tazers work? Hurts like hell, a bad afternoon but no real permanent damage, and you can be tasered again and again and live on without any damage, other than the psychological trauma.
posted by dancestoblue at 4:08 AM on August 4, 2013


More or less, yeah. Stun guns can put out tens of millions of volts, but at only 1 or 2 milliamperes, so no permanent damage, but plenty of "sweet merciful crap!"
posted by ShutterBun at 4:59 AM on August 4, 2013


I had a friend in college who had these odd round scars on the sides of his feet. One day, I asked about them. He told me that he was climbing a tree one day (as a kid) and he reached for a branch, which turned out to be a power line that was running through the branches of the tree. He said the blast he received ran straight through his body, from where he had grabbed the cable, and exited at his feet. The scarring was the result of the exiting current.

I guess he lived.

I, myself, inadvertently once placed my hand on a live 220 fuse receptacle. That was one of those "oh, shit, I can't believe I did that! oh, shit, oh, shit, oh, shit!!!!!!" moments.
posted by Thorzdad at 5:19 AM on August 4, 2013


It's the volts that jolt, but the mills that kill.

When you get a shock, you're completing a circuit through your body and, as been said, the amount of current rather than the voltage applied is what's going to do you harm. The thing that makes it possible for you to soak up a few thousand volts in one case while being offed by a hundred volts in another is the internal resistance of the voltage source - which depends on its design. Any system designed to deliver real power will have a low internal resistance and, if the voltage is high enough, will kill you. A high voltage system, no matter how high, that is designed for low power will leave you still able to express how impressed you are with what just happened.

Another factor is the frequency of the supply. At high frequencies - we're talking radio-type frequencies - current doesn't flow through the centre of a conductor (which, if that conductor is you, is a good thing) but around the outside, and the higher the frequencies the thinner the area through which it flows. That's called the skin effect and is one reason you can do spectacular things with Tesla coils without too great a risk of following Nikola into the aether. However, the power rule still applies, and there are a number of radio engineers with very impressive scars where an RF power amplifier delivered the goods into the punter instead of the cosmos. (And RF power amps tend to use tubes with many thousands of volts DC backed up by lots of amps, so are really interesting to work on anyway. There are pictures online. Don't go looking.)

But perhaps the best way to avoid getting an electric shock is to be a precocious kid with a penchant for ripping apart TVs and rebuilding the 25 kV circuits on a breadboard. Auto-Pavlovian conditioning? It works. Can't even lick a 9V battery these days.

But yes, an LED will glow at 25kV, irrespective of polarity.
posted by Devonian at 5:47 AM on August 4, 2013 [1 favorite]


Devils Rancher, you didn't take 50A at 220V. Sure you contacted a circuit capable of supplying that but you passed no more current than if you had contacted a 5A or a 4000A circuit. The voltage is a fixed quantity as is your bodies' resistance, ohm's law works out the rest without regard to what capacity circuit you are hooked up to.

I don't understand this stuff too well. It was a 3-phase conveyor dryer with a set of 50-amp fuses & each of the three fuses fed 1 of three heat panels. Each of the was wired directly to the high leg from the wall, and I guess overal the thing must have pulled something less than 50 amps, no idea what the overhead on those sorts of things are. All I know is it was 220 3 phase, & the unit just like it that I have now draws just under 50 amps at the cutoff sitch outside the unit. and a grabbed both sides of the fuse pretty firmly.
posted by Devils Rancher at 5:52 AM on August 4, 2013


The other had severe and permanent damage from touching the wrong bare wire with the back of his hand.

This is not a trick guaranteed to work 100% of the time.


it DID work - if he'd grabbed the wire, there's a good chance he'd be dead
posted by pyramid termite at 6:42 AM on August 4, 2013 [1 favorite]


Mine was touching the wrong part of the high voltage section of an old tube-based TV. This is where I leaned that those big capacitors in there hold their charge for quite some time after the thing is unplugged. Woke up on the floor some feet away.

Could be worse...a coworker at one of my first gigs had a son that had gotten a job at the local power company. Some time around 6 months on the job he completed a circuit with a 44KV transmission line. Burned his hands and feet off. He "survived" in the sense that it took more than a year before the damage, necrosis and infections finally caught up with him.
posted by kjs3 at 6:46 AM on August 4, 2013 [1 favorite]


Or you could, I dunno, wear gloves.

But perhaps the best way to avoid getting an electric shock is to be a precocious kid with a penchant for ripping apart TVs

Eegads. CRT's are deathtraps, with capacitors and static charges just waiting to fuck your shit up. Ripping them apart is a good way to NOT avoid getting an electric shock,really.
posted by ShutterBun at 6:53 AM on August 4, 2013 [1 favorite]


The most terrifying place I've ever worked was a bakery in midtown New Orleans. I was there in the late 1980's to install a scale indicator on a hopper which fed a mixing machine; the hopper was the scale, hanging from load cells about 15 feet in the air, and the scale indicator was an expensive stainless steel industrial quality device. Power neutral was connected internally directly to the stainless steel enclosure, which we bolted to the mixing machine frame. The mixer was bolted to the bare concrete floor and to a conveyor system that fed the batching hopper.

The electrician wasn't there yet, and we decided it would be good to power the system up so we could go ahead and calibrate the scale. There was an available outlet on the other side of the room, about 50 feet away, so my partner went to the truck and got an extension cord.

The moment we plugged the extension cord it began to HUM. After a few seconds we realized something was terribly wrong and unplugged it, drawing a good six inch long spark between the cord and receptacle. Probing with a meter revealed that the ground wires were at 110 volts with respect to one another. THE FUCKING GROUND WIRES. AND APPARENTLY UNFUSED.

When the electrician arrived we warned him of this and his response was oh yeah, there's stuff like that all over this plant, there's conduits hot with 110 and people done run temporary power taps off the hot conduits and those taps been there since JFK was President and I felt the blood draining out of my face.

This same plant had an area which was accessible only by a homemade one-person elevator approximately the size of a coffin, with no door. Taking the stairs was not an option. The coffinvator was the ONLY way up.

There is no place I was happier to see totaled by Katrina. They did rebuild it but this time they mostly seem to have followed code.
posted by localroger at 7:18 AM on August 4, 2013 [4 favorites]


I work for a company that makes laser printers/copiers. Xerographic voltages can be quite high but luckily very low current. Machines have a lockout safety switch that is intended to kill all the high voltage whenever a door is opened but during development and service there's a special tool you can use to keep things running. Touch the wrong spot and you'll find yourself sitting on the floor with aching muscles and no memory as to how you got there. And you will, eventually. I've seen lab techs with 30 years experience do it.
posted by tommasz at 7:27 AM on August 4, 2013 [1 favorite]


Turns out wiggling on bits and pieces of your car's ignition system is a good way to troubleshoot misfiring in damp conditions, but I wouldn't recommend it.
posted by sfred at 1:32 PM on August 4, 2013 [2 favorites]


I don't understand this stuff too well. It was a 3-phase conveyor dryer with a set of 50-amp fuses & each of the three fuses fed 1 of three heat panels. Each of the was wired directly to the high leg from the wall, and I guess overal the thing must have pulled something less than 50 amps, no idea what the overhead on those sorts of things are. All I know is it was 220 3 phase, & the unit just like it that I have now draws just under 50 amps at the cutoff sitch outside the unit. and a grabbed both sides of the fuse pretty firmly.

Ignore what the unit pulls, the appliance has a much lower electrical resistance than your skin and can be ignored for now, you were the limiting factor in this circuit, not the appliance. Ignore the fact the supply was three phase, you were only in contact with one leg (so, single phase).

If we work it out in really simplistic terms, we had a supply voltage of 220V and we'll say you had a skin resistance of 2000 ohms, which is possible. Using ohms law (V=I*R, I being current in amps) we get 220 = I * 2000. Which works out to a current of 110mA or 0.11A. This is pretty rough and ready but you can see that's a long way from the 50A rating of the supply. The fact that a heater was connected in circuit after you actually lowers this figure slightly.

The way to think about this is that the supply rating only tells you what can be supplied before the wiring in the wall and the electrical board will be damaged (in the absence of a circuit breaker or fuse). It tells you absolutely nothing about what will be drawn by a given appliance. In the case of electric shock you are the appliance.
posted by deadwax at 3:15 PM on August 4, 2013 [1 favorite]


A high voltage system, no matter how high, that is designed for low power will leave you still able to express how impressed you are with what just happened. ...
posted by Devonian at 7:47 AM on August 4


!!!!!
posted by dancestoblue at 5:23 PM on August 4, 2013


I once had the headphone output of an outboard soundcard feeding into a mixer which was connected to a PA. Inside which a crucial bit of ceramic had worn away (as later found). The singer usually screamed so we didnt know part of it was from the shocks off the microphone. There was a pop and a puff of smoke from the soundcard. Condensators exploded all over the inside.
posted by yoHighness at 5:41 PM on August 4, 2013


Sort of gave me a direct understanding of the effect of electro-shock therapy.

It's not the electricity that provides the therapeutic effect in ECT, but the seizure induced by the electricity (decent background here). An "electrical dose" below the seizure threshold provides no clinical benefit, whereas a dose above this threshold only increases adverse effects. A seizure induced via other means is just as effective—an early variant used drugs as the causative agent.
posted by dephlogisticated at 7:58 PM on August 4, 2013


220 volt U.S. AC power hurts quite a bit more than 120 volt power. With a 120 volt shock (to my right hand due to the left being in a pocket), I just keep working. With a 220 volt shock, I go take a break.
posted by Hello Dad, I'm in Jail at 10:18 PM on August 4, 2013


The thing to remember about electricity is that the load can't control the volts being pushed into it, but it does control how many amps it pulls.

That's why all those tiny lightbulbs in your car don't explode when connected to a car battery capable of providing hundreds of amps.

Using a hydraulics metaphor works pretty well. Volts are pressure, amps are the size of the pipes, and watts are the volume.

Our bodies will only draw the number of amps it can draw. Whether we connect ourselves to a 1 amp supply or a 1000 amp supply, the current that flows through us depends solely on the size and resistance of our contact points. (dry skin, wet skin, damaged skin, etc.) Dry skin is in the milliamp range. Wet skin is not. A 1mm contact point from grazing a wire will flow a lot less electricity than a bare foot on a wet floor and an open palm on a shorted refrigerator.
posted by gjc at 3:58 AM on August 5, 2013 [1 favorite]


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