In some ways yes it’s a bit overstated. Not everyone who gets shocked is going to die. In fact a very small number of people who get shocked will die. The important thing is that the number of people who will die isn’t zero.
Electricity kills you in one of two ways. It either screws up your heartbeat or it cooks you to death. Cooking you to death takes a fair amount of energy. However, a standard 120 V outlet will supply enough energy to do exactly that and under the right circumstances won’t blow the breaker doing it.
Screwing up your heartbeat takes a surprisingly small amount of energy, as little as about 5 mA. For those of you who aren’t familiar with electricity, that’s 0.005 amps. A typical 120 volt outlet can supply up to 15 amps before the breaker blows. A typical 30 watt light bulb draws 250 mA. If you’ve already felt rather uncomfortable touching electricity, you’ve already had more than enough current flowing through you to potentially kill you.
Just because it can screw up your heartbeat doesn’t mean it will, though. A lot of things come into play, like whether or not the current is actually going through your chest and exactly what point during the heart’s cycle it happens to be in when the shock occurs. There are a few points during the heart’s rhythm where it is much more sensitive to getting thrown out of whack than others.
The funny thing about your heart though is the way it works, once you get it screwed up, it tends to stay screwed up. So, unless someone is standing next to you with a portable defib unit, you’re in a big heap o trouble. Instead of beating, your heart just sits there and jiggles. Since it’s not really pumping blood at that point, very bad things tend to happen very quickly.
I admit your chances of throwing your heart out of whack are pretty low, but if you do manage to do it, the fatality rate at that pont is alarmingly high.
That’s why I said try to do stuff with one hand earlier. It reduces the likelihood of a hand to hand (i.e. across the chest and through the heart) kind of shock.
Actually, according to a good friend of mine who did a lot of work with early pacemakers, we couldn’t have picked a worse frequency to use for electricity. The heart is most sensitive to being thrown out of whack at frequencies around 50 or 60 Hz. Early studies with pacemakers used 60 Hz to stop the heart (on dogs) then let the pacemaker try and start it up again.
Very good point. I have heard that ‘hand to hand’ across the chest is much more dangerous. I think all my contacts have been just through two fingers on one hand.
Hmm…I thought it was lower frequencies that were really dangerous (15-30Hz), but I can’t find anything verifying it. At any rate, messing about with live circuits is definitely an unwise activity, lest you should short out your mortal coil. Even 110VAC is far from harmless.
Let me tell you about my experience with a neutral shock, and learn from my mistakes. As they say you won’t live long enough to make them all yourself.
OK, it was summer and very hot. I was sweating. This will become important in a few moment.
I needed to change out an 110V outlet located behind my stove. My stove is gas. I pulled the stove out a couple of feet, moved in behind it and while leaning against it started to take the outlet apart. Now usually when I do a switch/outlet change out, I do it hot. Meaning I do not turn the power off. (Note: kids do not try this at home it is not a good idea) I work with insulated pliers, and screwdrivers, and never touch any wire with my hands.
At this point my lovely wife says that she hates it when I work on a live circuit, and would I please turn it off. Wanting to keep my wife happy, I plug a lamp into the socket and ask her to holler when the light goes off. As luck would have it the very first breaker turned the light off.
I proceed to change the outlet. Now knowing that the box is dead (a little knowledge is a very bad thing) I am grab the green wire with my bare hands, no problem. I grab the one black wire with my hands, no problem. Now at this point there are two white wires left. I grab the one that goes out the top of the box, and all of a sudden my world lights up. It turns out that that neutral went to the lights in the kitchen, and I was now grounding 400 watts of incandescent light bulbs. So I had close to 4 Amps flowing up my arm, across my chest and out my back to the stove that was grounded via the gas pipe. You know the gas pipe that gets buried in the ground? Yeah that gas pipe. After what seemed like an hour or so (probably 1/2 of a second) my arm jerked free and I was no longer trying to do the frug across the kitchen. I think the reason that I was not killed was all the sweat on my skin. I think most of the current stayed on my skin and did not penetrate deep into my muscles.
Now I was pissed, and mad. Why the fuck did I get shocked by a “dead” circuit.
To finish the job I went out and turned off every single breaker, then I went back in and treated that damn white wire like it was made out of a mixture of nitroglycerin and plutonium. It was a couple of days before I could catch up with an electrician buddy who explained about shared neutrals, and how you can get shocked in a box you thought was dead.
Lessons to learn from my mistakes:
Turn off the damn breaker
After you have killed the breaker, test for voltage at each wire in the box.
2A. Before you use your voltage tester / meter, check a known live wire to verify your tester works. Murphy is always standing right behind you whispering in your ear “Go ahead, it’s OK, your tester if fine, you don’t have to check it, I got your back” Yeah right. If you have not verified that your tester works in the last two minutes, assume it doesn’t.
It doesn’t matter that you turned off the breaker, treat every wire as if it were a death threat, until you have verified that there is no voltage present. I don’t care what color the wire is, the last guy might have been color blind.
If you have a white in and a white wire out = DANGER! It might be a circuit covered by a separate breaker.
If you have any doubts, kill either the main or every single breaker, and then you know you have a dead box. It is easier to reset all the clocks then it will be to file all that life insurance paperwork.
You don’t have to be standing on wet concrete to the living fuck shocked out of you.
A common electrician saying is that 240V is the one that kills you.
Standard 120V is low enough that you can let go of the live wire; 480V is high enough to throw you and thus disconnect from the live wire; but 240V shocks your muscles enough that you can’t let go, but not enough to throw you off the live wire, so you just sit there and cook.
That’s basically true. Except that, it’s quite possible to be fatally shocked by any of these, and even much lower, if it happens to mess up your heart. Heck, the battery in your TV remote control could possibly do that, given the right circumstances.
Turning off the power and working on dead circuits is by far the best!
What happens when you get shocked is that your body is completing an electrical connection. The current will want to flow through the point of least resistance. What that means is that if you accidentally touch two bare wires with one hand, the current will flow from one wire to the other through the skin of that hand. The result is rarely fatal, but can cause damage to the hand - both contact burns and muscle damage.
But when you complete a circuit by holding one wire in one hand and one in the other hand, the current must cross through your body right at chest level. Some of it will flow through your heart, in proportion to the resistance of the tissues around the heart vs the tissues above it.
AC current at 60 hz can kill you if as little as 60 mA passes through your heart. House wiring is capable of typically providing up to 15A or 20A of current. So there’s plenty of current available to kill you dead. Be careful.
As long as the maximum current capability is over 50 mA or so, the maximum current capability does not matter. Only the voltage matters.
As an example, your car battery and your 120 VAC receptacle are both capable of sourcing 15 A with no problem. But the latter is much more dangerous from an electrocution standpoint. That’s because its voltage is higher.
So again, as long as the maximum current capability is over 50 mA or so, the maximum current capability does not matter when it comes to electrocution. Only the voltage matters.
I’ve heard that before too. I’m not sure how true it is.
One thing I know is that “medium” level shocks are much more dangerous. Lower level currents are much less likely to throw the heart into fibrillation, and higher level currents tend to make every muscle in the heart just contract. If this high level of current is removed, the heart usually starts beating again. It’s the medium level currents that are most likely to throw your heartbeat ouf of whack and kill you.
It would therefore make sense that 240 would be more likely to kill you than 120 or 480.
Were you shocked because you touched a hot conductor and you were standing on a wet tile floor? If so, then you were not shocked by 240 VAC. You were shocked by 120 VAC.
Almost all electrocution incidents occur because a person touches one hot conductor and earth ground. On a 240 VAC circuit (clothes dryer, range, central air, etc.) each hot leg is only 120 VAC relative to earth ground. So if you’re working on a 240 VAC circuit, and you touch a hot leg when you’re grounded (which is usually what happens when a person gets shocked when working on a 240 AC circuit), you will get shocked by 120 VAC, not 240 VAC.
The only way to truly get shocked by 240 VAC is to do the following:
Ensure you are ***extremely ** * well isolated from earth ground. This is more difficult than it sounds; it means you need to be wearing very thick, rubber-soled shoes, and no other body part can be touching anything.
Touch one leg of a 240 VAC circuit with one hand. Because you are extremely well isolated from earth ground, you will not feel a shock.
Touch the *other * leg of the 240 VAC circuit with *other * hand.
Zap.
Again, this is a pretty rare thing to happen. The primary reason is that a person will usually feel a tingle during step #2 (even if they’re wearing rubber-soled shoes!), realize something is wrong, and hence will *not * proceed to step #3. Why? Because as mentioned, it is very difficult to be *extremely * well isolated from earth ground. Even if you’re wearing shoes with *infinite * resistance, there will still be capacitance. The frequency is 60 Hz, and the rubber soles act as the dielectric of a capacitor. Make a few quantitative assumptions, do the math, and you can calculate how much current will flow through your body strictly due to capacitive coupling.