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When I was about 10 years old playing with lamps, I accidentally picked up a wire completing a circuit for a lamp plugged into the wall (120 V AC U.S. standard). I'm not sure if it was the hot or neutral wire, but I had completed the wire from hand to hand. I had a shock and dropped the wire in slightly less than a second.

According to what I see online, which says milliamps can kill me, how did I survive for this long, with no burns or negative health effects? I remember immediately running up to my mother and saying I just got shocked by a house socket with a big grin on my face! (she was not happy!)

Mathieu K.
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JavaProphet
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    Have you measure [your] resistance from one hand to the other? – Tyler Nov 23 '16 at 16:54
  • @Tyler No, but my hands were dry. I was average size for a 10 year old, so probably lower than an adult? – JavaProphet Nov 23 '16 at 16:55
  • http://electronics.stackexchange.com/questions/206893/why-can-sticking-fingers-in-an-electric-outlet-kill-you/206953#206953 – Ecnerwal Nov 23 '16 at 17:08
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    I think most EEs have received at least one shock and possibly several. Yet we live to tell the tale. It tends to be the lethal shock that hits the news stand but the truth is that most shocks are not lethal - just painful at the time and a true learning experience. – JIm Dearden Nov 23 '16 at 18:35
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    If normal household voltage (and I count the 220/230V in Germany in) commonly killed people many of us wouldn't be reading this ;-). – Peter - Reinstate Monica Nov 23 '16 at 20:48
  • I remember putting a pin through the AC live output and had a small shock. It wasn't big because I was upstairs. – Bradman175 Nov 23 '16 at 23:57
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    How does being upstairs cause the shock to be small? – JDługosz Nov 24 '16 at 06:15
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    @JDługosz Gravity – Thomas Nov 24 '16 at 07:28
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    @Thomas you will have to elaborate or clarify. The electricity in an upstairs outlet is no different from that in a downstairs outlet. Are you describing sticking a metal object into a wall outlet, or something different? – JDługosz Nov 24 '16 at 07:36
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    @JDługosz I am just being a troll, note I didn't post the original comment. – Thomas Nov 24 '16 at 08:38
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    I got shocked multiple times as a kid. With 220V, I have naturally sweaty palms and low body fat - all the factors stacked against me, and it still was nothing more than adrenaline rush. – Agent_L Nov 24 '16 at 08:52
  • Well here in Europe we have 230 volt sockets... – RudolfJelin Nov 24 '16 at 15:21
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    Popular believe != truth. Since life and death are such a big deal to most humans, obviously if something *could* kill you, some people are going to turn that in to *will* kill you. – AbstractDissonance Nov 24 '16 at 16:52
  • I got shocked on a pipe from a colour TV cathode tube (fisure in isolation, old TV). It felt like a hammer straight in the heart, left me panting, but I was lucky enough to have been dirty (while cleaning around the pipe), dry (dust/dirt keeps hands dry) and my skin resistance is very high (could test socket for 230VAC with thumb and index and barely feel it, then; now I'm older). Also got it from a black-white TV, in college. And lots of times from mains. Yet, I still live, and I'm nromal, not dylsexic or aynthign... – a concerned citizen Nov 25 '16 at 16:13

6 Answers6

32

You got lucky.

Electrocution isn't an exact science. There are multiple things which make a difference:

  • The current which flows through a person depends on the resistance. That in turn depends on whether the skin is wet or dry, the area of skin in contact with the wire, and a lot of other biology things.
  • The resistance of the things completing the circuit - whether you're touching a metal radiator, or standing on a rubber doormat for example.
  • The path of the current through the body matters too, it is currents through the heart that are dangerous, so getting a shock leg-to-leg is less risky than left arm to right leg, for example.
  • Release time. If you drop the wire quickly, there is less risk of damage. The automatic response to let go of the painful thing might happen quicker or slower depending on all sorts of biological things.
  • Health. Some people are just more susceptible to shocks than others. This might depend on build, body fat percentage, or just a pre-existing heart condition.

And of course voltage, source resistance and frequency of the source you're touching also matter. All in all, US mains is in the range where it's not guaranteed safe, nor guaranteed to kill, so it comes down to the factors above, and a healthy dose of luck.

Don't try it again.

Dessa Simpson
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Jack B
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  • Actually the reactance and d=80 of skin moisture is just as important if not more important. Consider that a tiny arc occurs and the contact current spike charging that skin is broad spectrum determined by dV/dt in picoseconds and the impedance of a finger tip is ~300pF applied to this current impulse spectrum and compare with 100k over this spectrum – Tony Stewart EE75 Nov 23 '16 at 18:48
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    "automatic response to let go of the painful thing" — with shocks that can be counteracted by muscle contraction caused by the electric current, so you end up holding on to the wire. Electricians tend to use the outside of their hands (after checking for liveness in other ways typically) for just this reason! – Stephen Kitt Nov 23 '16 at 21:59
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    It's also good practice to use only one hand if possible when working on circuits that may be live (or may have large charge built up in capacitors, like CRT televisions), so that if you do get shocked, it won't cross your heart. – BlueRaja - Danny Pflughoeft Nov 23 '16 at 22:58
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    @StephenKitt It's only true if you grab a busbar with your full hand, like weightlifter handling a barbell. If you handle a house-sized wire with tips of your fingers, then your arm muscles twitching back are way more powerful than your fingers' grip. – Agent_L Nov 24 '16 at 08:51
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    @Agent_L with the tips of your fingers yes! I got my electrical training while working for a distributor so grabbing busbars was a thing (for some of my colleagues anyway), I guess the training would have erred on the side of caution. I would have thought grabbing *e.g.* a 16A cable while connecting an oven would be enough (assuming egress back through the cable rather than ground)... – Stephen Kitt Nov 24 '16 at 08:58
  • I hike a lot, and I've lost count of how many times I've had to explain to people why, if all the other ways of checking have proved inconclusive, you test whether a fence is electrified using the back of your finger, **not** the palm of your hand. Most fences don't put out a high enough current for you to get stuck clenching a fist around it, and most of them zap in short pulses with time in between for you to let go (both legal requirements, I'm pretty sure) but there's always some redneck who just hooks a car battery to a couple of wires and calls it a day. – anaximander Nov 24 '16 at 19:52
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There is a big difference between a current that is guaranteed to be safe and one that is guaranteed to kill.

In order to kill you there has to be either a current flow through the heart (eg. from hand to hand but there may be other paths, such as hand to leg) and/or you have to cook your body enough to cause fatal tissue damage.

The most dangerous situation is if your hands are wet (or sweaty) and the voltage is high, and there is a path through the core of your body. Avoid working on live voltage, and if you must, keep one hand in your pocket. Or, as an Engineer classmate of mine who worked for an electric utility advised, keep both hands in your pockets and let the technicians do it.

Spehro Pefhany
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    I once got a shock from the UK 240V AC mains, by holding a wire connected to line in one hand, and another wire connected to neutral in the other. I dropped the wires very quickly, but it was rather unpleasant. My chest muscles ached for some time. – Leon Heller Nov 23 '16 at 17:10
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    @LeonHeller Good that you survived. As a kid I got an 800VAC shock that was confined to one hand, but the wires penetrated my skin (a transformer with a pointy terminal strip fell over onto my right hand). The ~10lb transformer was rendered airborne by muscle contraction and that ended the shock, but I still have a small visible scar many decades later. Very unpleasant. – Spehro Pefhany Nov 23 '16 at 17:42
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    I guess there is not even a "guaranteed to kill" level, people have survived straight lightning strikes, power pole accidents and whatnot, and even .... intentional application of such doses doesn't always seem to work on the first try. – rackandboneman Nov 24 '16 at 09:13
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    +1 also for "keeping both hands in your pockets". That's great advice!! – Ricardo Nov 24 '16 at 10:56
  • Let the technicians do it: presumably not because you want them to bear the risk instead of you, but because they have better training and _way_ more experience, and so are less likely to hurt themselves. – Mathieu K. Nov 25 '16 at 07:11
  • @SpehroPefhany, I'd suggest changing "guaranteed to kill" to "likely to kill". Danger implies high risk, not a guarantee: working with live electricity is dangerous because poses a high risk to your life/health, not because it's _guaranteed_ to kill you. – Mathieu K. Nov 25 '16 at 07:18
  • @MathieuK. I think he's right with "guaranteed to kill". It looks like OP was under impression that mains shock carries a kill guarantee, so this sentence is aimed at that misconception precisely. – Agent_L Nov 25 '16 at 08:46
  • @SpehroPefhany, I was taking the rest of the answer as an explanation of what "one that is guaranteed to kill" means. Answerer, it looks like your intent may be ambiguous. – Mathieu K. Nov 25 '16 at 14:49
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Milliamps can kill you, but that doesn't mean it will kill you.

There are countless variables involved, one of the most important of which is your skin resistance (which limits current significantly if your skin is dry). Also, it sounds like the current flowed through your arm, down your side, and down your leg to ground (that's the easiest path in most cases to ground).

If you had touched the neutral with one hand and the live with the other, the easiest path for the current would be across your chest, which means across your heart. This is where things get dangerous. If current flows through your heart it has a higher chance of causing fibrillation (your heart stops).

That's the idea behind the one-hand-in-pocket rule when working on live electronics. If you keep one hand in your pocket and only poke around with one hand, it helps prevent you from coming into contact with the live circuit with both hands which provide a path across your heart.

Marcus Müller
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DerStrom8
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    Wouldn't a current running through your left arm and down your leg also get dangerously close to your heart? Which is why I leave the high-voltage/amperage stuff to the pros and I only mess with low voltage DC. :-) – cbmeeks Nov 23 '16 at 18:24
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    @cbmeeks your heart is actually pretty well centered in your chest, despite the common misconception that it is closer to the left side. – DerStrom8 Nov 23 '16 at 18:26
  • then it wouldn't really matter about "hand to hand" or "hand to leg". Either one is going to get close to the heart. That is..assuming equal high voltages in both scenarios. – cbmeeks Nov 23 '16 at 18:46
  • @cbmeeks No, it absolutely does matter. "Hand to hand" takes the current right *across* your heart. "Hand to leg" carries the current *away* from your heart. It's not current "near" that heart that's important, it's the current THROUGH the heart – DerStrom8 Nov 23 '16 at 18:56
  • what if I had the wire in my left hand but was standing on my right foot with my left foot raised? Or, say I only had one leg in the first place. Point is..it's not an exact science. – cbmeeks Nov 23 '16 at 19:42
  • @cbmeeks No it is not an exact science, nor am I claiming it to be. I'm simply making a generalization which is *generally* correct. That's all this question required for an answer. – DerStrom8 Nov 23 '16 at 19:45
  • @cbmeeks Strictly speaking high-amperage stuff at low voltage won't electrocute you. But not many things use high amperage and low voltage. (The internal parts of computers come to mind; I have a power supply rated for 25A @ 5V) – user253751 Nov 23 '16 at 21:33
  • @immibis By 5v do you mean low voltage AC or DC. Because amps produced by AC and DC are two different beasts. – Bacon Brad Nov 24 '16 at 00:12
  • @baconface At 5V not very many amps will go through a person, AC *or* DC. – user253751 Nov 24 '16 at 00:13
  • @immibis There is still a *major* difference of getting 25 amps on AC or DC. The two at the same voltage and amps are not comparable. I am just mentioning this since 5v AC is not a common voltage. So while your 5v 25A DC power supply may be minor 25A on AC is no joke. – Bacon Brad Nov 24 '16 at 00:16
  • @cbmeeks Be careful with words, everything below 1kV is "low voltage" : ) The safe voltage is "ultra low". – Agent_L Nov 24 '16 at 08:54
  • @baconface We're talking about electric shock here - *you will not get 25 amps* through yourself at that voltage. Unless you do something dumb like sticking electrodes into your bloodstream. Point is, when working inside a desktop computer you don't need to take any special precautions to avoid electric shock. I've never heard of someone getting shocked from 5V or 12V. (You do need to take precautions to avoid damaging the computer, but that's a different story) – user253751 Nov 24 '16 at 10:21
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The only reason you felt very little is that your skin was very dry at the time relative to most people. i.e. conductivity was low , which is the inverse of high impedance.

Skin have two fundamental electrical properties as do all materials in the universe. They are either mainly "conductors or insulators". All metals are conductors and all insulators are dielectrics. The skin body is mainly an insulator with conductor properties when moist due to water and also salt.

Current at low frequency 50/60Hz affects what you feel and depends on 2 factors;

  • The property of the dielectric constant and frequency/voltage spectrum of source
    • compared to air , water is 80x more dense in ability to store/conduct charges
    • general test standards use human models models (HBM) for a human finger tip are 100 or 300pF but increases with surface area of contact and used for static discharge purpose (ESD) susceptibility tests.

  • the property of resistance which applies to DC and AC

    • the biggest factor is skin moisture content, dielectric constant is ~80
    • the second factor is ion content such as dissolved salt in sweat, which affects mobility of charges and thus resistance which can vary from 10M for very dry skin to 50k for moist fingers to <10k for your tongue
    • again surface area affects resistance as well as moisture & salt such as blood, plasma and why the heart in an operating room needs very little current for surgeons to start or stop the heart in surgery yet large watt-seconds when applied to contact grease to the chest.
    • This is also why a glass of tap water heats up much slower compared to salty water in a microwave oven in 60 seconds.

  • International Equipment safety limits are 500 uA for 50/60 Hz for equipment leakage to ground in case of a ground fault. This does not mean you can't feel it, but it won't hurt you.

So what you felt may have been slightly more or less than this 0.5mA (500uA) depending on severity.

Tony Stewart EE75
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4

The human body typically has a high resistance when it is dry. As quoted below, it can be as high as 100,000 ohms. So the current going through your body would only be 170 V / 100,000 Ω = 0.0017 A. This is only 1.7 mA and the "let-go" current is right in between 10-20 mA.

The NIOSH states "Under dry conditions, the resistance offered by the human body may be as high as 100,000 ohms. Wet or broken skin may drop the body's resistance to 1,000 ohms," adding that "high-voltage electrical energy quickly breaks down human skin, reducing the human body's resistance to 500 ohms."

There are also a lot more variables involved, such as how long you were touching the wire for. What is the resistance from one hand to another. What were you wearing when you got shocked? One of the other things to consider is where the current actually flowed through your body.

Peter Mortensen
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12Lappie
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1

It is not the current itself which is dangerous (unless under very high voltage, thousands of volts, where one gets burnt by the current), but the temporary effects on the nervous system which is basically using electrical discharges to carry informations and commands from/to the brain and the muscles.

Electrocution can kill you because your LUNGS CANNOT function properly (they are 'paralyzed'), and you die of suffocation after a while, or because the HEART stops because it loses the beat commands. This needs either a big shock (to stop the heart, still much more than what can be achieved with 110V our 220V in normal isolation conditions) or a long exposure so that you would suffocate.

Thus it is perfectly normal that the electric shock didn't kill you.

And as everyone else, I can testify that I got shocked a handful of times with 220V AC (my mistakes) and that I am still living. But better avoid it.

Mathieu K.
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Mike
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  • What are "normal isolation conditions"? As OP stated, she/he suffered an electric shock with closed circuit "hand-to-hand". Lethality is here roughly 2%. The current is of course sufficient to stop your heart instantly. But there are other factors contributing to the probability of ventricular fibrilliation. So the OP in fact was just lucky the AC current didn't hit the vulnerable phase of the hearts cycle with sufficient amplitude. – Ariser Nov 24 '16 at 13:47
  • The muscles (without conscious thought) caused the circuit to be broken. Heartbeats were not held at bay long enough to matter. 120VAC in the states is seldom lethal it just startles. 240VAC hurts though, and its pretty good at ruining pliers because the resistance is essentially 0 ohms. – boatcoder Nov 24 '16 at 21:00