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I managed to shock myself and wanted to see how dangerous that shock actually was to me (to figure out how much of an idiot I was). So I looked around for information on how to 'calculate' the various electricity related figures (mainly voltage and amperage) and at this point I'm more confused now than I was when I started...

I often came across the "it isn't the voltage that kills you, it's the amps" quote, but it seems quite clear that the statement isn't really true from what I've seen:

A car battery (low voltage high amps) won't kill you because the voltage is very low and won't 'penetrate' the skin, a taser (high voltage low amps) also won't kill you because despite the high voltage and amps are so low that it won't do much real damage, and even a high voltage high amp device may not kill you if the 'exposure period' is small enough...

So I've got no good idea on how to 'judge how dangerous a shock can be' aside from knowing it involves time, voltage, and amperage in relation to each other. Amperage seems especially confusing to me because usually people throw out the I=V/R formula to estimate how many 'amps your body experienced', but this formula only seems to consider the voltage of the source, since a source with 12 volts / 1 amp and 12 volts / 1k amps would work out to be the same (I'm sure that my usage of this formula is wrong...).

So voltage won't outright kill you and amperage won't either (well, not without extreme values), so what is a formula that can actually approximate the risk? Does it involve watts perhaps?

*A little more info since Rod Vance asked for it: while I was moving a circuit board I adjusted it a bit in my hands and I think when doing so my thumb touched the terminals of a Capacitor and I got a bit of a 'buzzing sensation' (220V/300uF specs). Nothing major (hopefully)...

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    $\begingroup$ +1 for trying to learn from your mistakes. :) I've been wondering about this myself (preemptively rather than reactively). $\endgroup$ – Fine Man Oct 20 '16 at 3:47
  • $\begingroup$ This is fairly informative. $\endgroup$ – Fine Man Oct 20 '16 at 3:53
  • $\begingroup$ You should probably describe your shock a little. Internal burns from current paths through muscle tissue - eg from currents entering and leaving the same hand - are often painless and the body has a hard time absorbing the burnt, dead tissue inside you if the burn is big (and it can be without much surface sign). The condition can lead to necrosis and gangrene: you should probably seek medical advice if the source was of a high voltage with low source impedance. If you were aware of it, you should get it checked out anyway. $\endgroup$ – WetSavannaAnimal Oct 20 '16 at 7:15
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    $\begingroup$ Any electrical shock (not static electricity) should result in a trip to the doctor - even if you feel fine your heart may be going in to fibrillation. Voltage, current, frequency (ac vs dc), where you were shocked, the path through you, if it was arc flash, ... these all impact what actually happens to you. $\endgroup$ – Jon Custer Oct 20 '16 at 13:04
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    $\begingroup$ For people in good health any shock, not static, should result in a trip to the doc is being very cautious. If I got a zap off a spark plug wire and then went to the doctor, I am pretty sure I would be asked how do you feel. Once I said fine, I would likely see a puzzled look on the doctor’s face followed by a general examination and that would be followed by a 150.00 bill about two weeks later. I guess that’s a sure way to make sure that the shock does do some damage. But I am not a doc so what do I know? $\endgroup$ – Lambda Feb 11 '18 at 19:58
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This question is very complex and any complete answer would probably need to be book sized. There are many effects of electricity on the body and they all play a role in how dangerous any shock is. As others have noted, the important factor is current. However, besides intensity, frequency,duration and location are important. Also, a current that goes straight through a finger will hurt a lot, but be much less dangerous than one that goes through the heart.

Regarding the main effects of current on the body, they can be divided in thermal and non-thermal effects. Thermal effects mean that due to the resistance of the tissues through which the current flow, the tissues heat up and are eventually damaged. Watts, as mentioned in the OP is very important in this type of effects. Non-thermal effects are due to disturbance of the body's function through interaction with cells that normally respond to electrical currents, the nerves and muscles (the heart is a muscle also!). This is where it gets complicated.

There have been accounts of people on the electric chair surviving a first shock, but in which the current caused all muscles to contract so violently that bones were broken. Also, while a shock can send you in fibrillation, a defibrillator uses a carefully shaped shock to reinstate normal heart beating. While you would think that passing a current through the brain would not be a good idea, that is exactly what electroshock therapy does. Of course, this last one was abused, but my understanding is that in some cases, it's the only thing that remotely works for some patients. So, the effect of a specific accidental shock will be highly context dependent.

Another important factor in electrical shock is skin resistance. An intact dry skin has much larger resistance than a cut skin. For a given voltage, intact skin will allow a much smaller current to flow through the body than injured or wet skin.

Regarding the difference between voltage/amperage, one has to be very careful. A car battery can provide a very large amperage if required, but the voltage is still only 12 Volts. If you insert a large resistance between the terminals of the battery, the battery will not suddenly provide 100 amps because it can. Voltage is the same. You may have a very large voltage, but not enough charge to provide a large current. To get damage from an electrical shock, you need enough voltage to create a sufficient current through the body, and capacity to provide that current for enough time.

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I often came across the "it isn't the voltage that kills you, it's the amps" quote, but it seems quite clear that the statement isn't really true from what I've seen:

It's the current which flows through you which kills you, which is measured in amps. But whether the current can flow through you depends on the voltage, too, and the source of the current.

people throw out the I=V/R formula to estimate how many 'amps your body experienced', but this formula only seems to consider the voltage of the source, since a source with 12 volts / 1 amp and 12 volts / 1k amps would work out to be the same (I'm sure that my usage of this formula is wrong...).

Ohm's law (the name of that formula) doesn't apply to the human body. Low voltages can't penetrate the skin, so the human body is "non-ohmic" (Ohm's law does not apply). Mains voltage (100-240V) is enough to penetrate your skin. Exact danger depends on the current path. The most dangerous is said to be from one hand to the other, where the current goes through the heart, zapping it and preventing it from functioning correctly.

So voltage won't outright kill you and amperage won't either (well, not without extreme values), so what is a formula that can actually approximate the risk? Does it involves watts perhaps?

Voltage alone won't kill you either, the small shock you get when you get out of a car or touch a door handle after walking on a carpet is several thousand volts. But the small static charge means only a tiny current flows.

Mains electricity can cause a very large current to flow through you, which is why it's dangerous.

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    $\begingroup$ AC vs DC current is also a factor: see en.wikipedia.org/wiki/War_of_Currents $\endgroup$ – DJohnM Oct 20 '16 at 4:23
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    $\begingroup$ Mains electricity causes a very small current to flow through you but 50mA can be fatal. The AC is dangerous - when it makes your heart try and beat at 50/60hz. $\endgroup$ – Martin Beckett Oct 20 '16 at 5:00
  • $\begingroup$ This answer is promising and mostly correct, but is incomplete until the information about the frequency response of the heart is edited in. $\endgroup$ – rob Oct 20 '16 at 5:48
  • $\begingroup$ There are lots more things which could be said here, I have no idea about the frequency response of the heart or about AC versus DC shocks. The Wikipedia article on electric shocks claims that AC is more dangerous than DC by a factor of two, but gives no citation. As far as I know, 100V or more DC is actually more dangerous than AC in practice and requires special equipment. It's not something one encounters around the home. $\endgroup$ – Suzu Hirose Oct 20 '16 at 8:56
  • $\begingroup$ I'm still confused at how Amps get factored in....Usually a 'guide' will say something about touching a voltage source of xx volts then use I=V/R, but surely if the source carries 1 amp vs 15 amps that should get factored in somewhere no? $\endgroup$ – Joe Oct 21 '16 at 11:26

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