Do the amps or volts kill? - Page 1
Forum section: electronics / general

author: tyguy2
author_rank: Unknown
timestamp: June 10, 2015, 04:03:29 pm
content: I've gotten myself into an argument with a friend over whether amps or volts kill. I figured I'd ask the forum.

author: c4757p
author_rank: Super Contributor
timestamp: June 10, 2015, 04:09:01 pm
content: Neither. Amps and volts are units, the words you're looking for arecurrentandpotential. More accurately,potential difference, an important distinction when discussing electrical safety.Anyone who definitively answers either 'current' or 'potential' is a wally. Both are linked by V = IR.

author: tyguy2
author_rank: Unknown
timestamp: June 10, 2015, 04:10:37 pm
content: That's what I said

author: suicidaleggroll
author_rank: Super Contributor
timestamp: June 10, 2015, 04:13:33 pm
content: https://www.eevblog.com/forum/beginners/what-kills-people-current-or-voltage-or-something-else/

author: tyguy2
author_rank: Unknown
timestamp: June 10, 2015, 04:25:36 pm
content: He's showing me this video:

author: c4757p
author_rank: Super Contributor
timestamp: June 10, 2015, 04:27:54 pm
content: He didn't watch the video himself then, because Mehdi said what I just said (and you agreed with that). The two are inextricably linked.

author: tyguy2
author_rank: Unknown
timestamp: June 10, 2015, 04:36:38 pm
content: I have no idea. He isn't responding to texts either...Thanks for the help.

author: Richard Crowley
author_rank: Super Contributor
timestamp: June 10, 2015, 04:57:58 pm
content: For a very simplistic argument with someone who knows nothing about electricity, if I had to select ONE, I would pick voltage.Reason: Human skin is rather an insulator and it takes higher voltage (or conductivity-enhancing things like moisture, etc.) to "break-through".It doesn't require much current to do the damage once you "get inside".6V @ 1000A is hardly dangerous unless you put a screwdriver or wrench or something across the terminals.And then the danger is not the electricity, but the HEAT that the power generates.OTOH, 1000V @ 6A is ALWAYS dangerous. And just as dangerous at 0.006ACould you kill someone with 6V? Yeah, maybe if you jammed a pair of electrodes into their cardiac muscle.But then you probably wouldn't need the 6V.

author: Tandy
author_rank: Frequent Contributor
timestamp: June 10, 2015, 05:18:05 pm
content: It probably comes from a oft quoted cliché "It's the volts that jolts and the amps that kill".Clearly it is misinterpreted as meaning that current is the critical factor rather than the original meaning that it is not the voltage alone but sufficient current must also be available to cause injury or death in a ordinarily healthy person.

author: AG6QR
author_rank: Frequent Contributor
timestamp: June 10, 2015, 06:39:09 pm
content: Voltage and current are related by Ohms law, of course. You can't push current through a person's body unless you have enough voltage to overcome skin resistance, which varies widely with moisture and other factors.Having said that, the damage done is most closely related to the level of current that actually passes through the muscles. If you've ever been zapped by a spark from walking across a carpet and touching a doorknob, you've survived a shock of thousands of volts. There wasn't enough current behind it to do damage, though. A Van de Graaff generator will easily produce hundreds of thousands of volts, but the current is so low that it's safe enough that science museums regularly allow children to be zapped by them in demonstrations.But put between 100mA and 200mA through your heart muscle, and you'll die. The amount of voltage required to achieve that 100mA to 200mA will vary widely with conditions. A 100mA shock produced by a 50V source through wet skin at low resistance is as fatal as a 100mA shock produced by a 1000V source through dry skin.I regularly work around a 12V car battery capable of supplying hundreds of amps, but I don't need to take extraordinary precautions to safeguard my life, because, while 12V may be able to push lots of current through a starter motor, it's not enough voltage to push any significant current through my dry skin. (I do want to be careful not to short out the battery with a wrench or other metal tool, because it could cause enough heat to cause the battery to explode and splatter acid around.)So saying it's either "voltage" or "current" is a gross oversimplification. But because the current level required to kill is more constant than the voltage level required to kill, I'd vote that the "current" oversimplification is slightly more justified than the "voltage" oversimplification, even though neither tells the whole story properly.

author: LukeW
author_rank: Frequent Contributor
timestamp: June 10, 2015, 07:06:29 pm
content: It's the "amps that kill", but apply Ohm's law to that and you'll see that it's a combination of three things "that kill" - the supply voltage, the source impedance and the skin resistance.As well as the amount of current that is routed through critical parts of your body, eg. heart.

author: tyguy2
author_rank: Unknown
timestamp: June 10, 2015, 07:14:44 pm
content: Ok, so he finally replied to my texts, yet, even though I have shown him this thread, still FIRMLY believes that it's ONLY the amps that kill.

author: tyguy2
author_rank: Unknown
timestamp: June 10, 2015, 07:15:56 pm
content: I guess some people can't accept that they are wrong. Thanks for the replies, I really appreciate it.

author: TimFox
author_rank: Super Contributor
timestamp: June 10, 2015, 08:38:20 pm
content: Amps kill, but the voltage required to produce that current depends on the body state, including skin moisture.You can't simultaneously apply a specific current and a specific voltage toanyload, linear or non-linear.If you use an old-fashioned lab supply with proper voltage and current control, and set it to (for example) 100 V and 1 A, one or the other (not both) of these settings will limit the voltage or current through the load. With a 200 ohm load, you will get 100 V and 0.5 A.

author: calexanian
author_rank: Super Contributor
timestamp: June 10, 2015, 08:43:44 pm
content: It has been conclusively proven (I remember it from a NEC safety class) that current is the method of nervous damage. Current of just a few milliampers can disrupt nerve signals. 5 ma in path through the heart can cause enough nerve signal confusion to disrupt a heartbeat. 1ma is perceived as painful. Depending on current path, such as through an extremity where the centeral nervous system is not as effected and conduction is not through your chest area, sufficient current and voltage can occur where burns can result. Generally though your neurons controlling your heart are scrambled by then.

author: TheAmmoniacal
author_rank: Unknown
timestamp: June 10, 2015, 09:28:43 pm
content: To me this question is very much like the "do current pass through a capacitor?" question. Practically speaking I'd say volts kill you, technically speaking I'd say current does.Death by an electric shock is by disrupting the regular rhythm of either the diaphragm or the heart. I don't think it matters how much voltage you apply across it, as long as a current larger than about 5 mA passes across - you have the potential to disrupt the rhythm - and if it doesn't recover you're dead.In a practical setting you will be a human being made of dry skin and blood, and to get any significant amount of current across your chest - you will need a high voltage to overcome the resistances imposed by your body. (Rough values pulled out of my ass: average layer of dry skin is 100k ohm. Resistance across the wet tissues of the body: 300-500 ohm)An interesting phenomenon is that low currents (<5 mA) through muscle tend to have a flexing effect (gripping/freezing), while larger currents (>20 mA) tends to do the opposite (extension/open).(All that said though, you must be unlucky to die from electrical shocks, even if they are high voltages - and even if current do cross your heart and diaphragm. Not all currents will be disruptive, and even if they are - the rhythm can recover. And most often you will be able to let go very quickly)

author: Wilksey
author_rank: Super Contributor
timestamp: June 11, 2015, 12:27:33 pm
content: Of course current kills, but only if used correctly...uh I mean incorrectlyImagine current / Amps whatever you want to call it, as being a knife.Imagine voltage / potential, being a driving force, such as a person's hand (holding said knife).If that person's hand touches you with a knife, chances are it won't kill you, it might sting or graze depending on the force of the touch (call it 5 volts), if that person decided to use a large force (say 230 volts of "force") chances are if that knife is aiming in the correct place, it will kill you, best case it's going to be painful and messy and ruin your day.Yes, it's over simplified, but it explains why you would need both elements for your friend to understand.

author: VK5RC
author_rank: Unknown
timestamp: June 11, 2015, 01:01:50 pm
content: V=I.RWhat actually kills most people is a small voltage (and current) across some of the myocardial (heart muscle) cells esp if they are in the recovery phase of contraction. This voltage triggers the voltage dependant Ion channels (K out, Na in) and this then spreads to nearby recovering myocytes. This can generate a circular pattern of triggering (circus movement) and this is one of the more common methods of inducing lethal cardiac arrhthmias esp Ventricular Fibrillation. In this state the heart doesn't pump, if not defibrillated ( or by chance spontaneously) a few seconds later you pass out, a few minutes later your brain is mush.Goodnight Irene!

author: con-f-use
author_rank: Unknown
timestamp: June 11, 2015, 01:11:41 pm
content: As the video said, technically the bullet (=current) kills you. However, everyone would rightly blame the shooter (voltage). I say it's the current path and timing that kills you!

author: all_repair
author_rank: Frequent Contributor
timestamp: June 11, 2015, 01:34:34 pm
content: The answer the poster wanted is given many time here. But winning an argument for a life and death matter is insignificant. In the context of practisioner, for those who are still alive dealing with high voltage and high current, day in and day out, hopefully can be a proof that neither voltage or current that kills. It is the carelessness, stupidity, absent of respect and absent of fear towards the electricity, safety and procedure that kills. People that are the most dangerous are not those that do not know, or the expert, they are those that know just enough to be dangerous and yet refuse to, or humble enough to realise that there are many things they do not know that they do not know. Please watch out for them to protect yourself and to guide them well.

author: VK3DRB
author_rank: Super Contributor
timestamp: June 11, 2015, 02:25:08 pm
content: About 5 years ago, I had this argument with a very opinionated (and possibly a little arrogant) experienced EE with a PhD. I told him that as little as 20mA through your body could kill you. He responded, "!!! You need at least a couple of hundred milliamps across the heart to kill a person." To avoid the argument escalating, I let it go and forgot about it. A couple of hours later he came up to me to apologise and admit he was wrong. He had done some research. I respected him for doing the research and having the humility to apologise.The current through your heart muscles is a factor of the voltage applied and the moisture and salt content on your skin at the contact surface. A lethal situation is to be hot and sweaty on the hands (but not so much your torso), and put 240VAC active in one hand and neutral in the other hand. The current across your heart will likely kill you. A good test is to get your DMM, lick your fingers and hold a lead in both hands and measure the resistance.Your blood which is somewhat saline has a resistance of, give or take, a few hundred ohms around your body. You urine has even a lower resistance, so having a leak against an electric fence at a farm is not a good idea, despite it not killing you.You will find 20 x nine volt batteries plugged together in series could kill you if you touched each end with sweaty hands (DC is more dangerous than 50 or 60 Hz AC by the way). Don't try it!I knew a friend of my brother who climbed a 220KV power line tower. He was electrocuted and died instantly.

author: fubar.gr
author_rank: Unknown
timestamp: June 11, 2015, 02:52:19 pm
content: Quote from: VK3DRB on June 11, 2015, 02:25:08 pmAC is more dangerous because the human body has capacitive properties and therefore the impedance is much lower than DC ohmic resistance. See some of Electroboom's videos for confirmation.9 Volt batteries have a huge internal resistance. Stringing 20 of them together will multiply the total voltage by 20, but same goes for ESR. Yes, under specific circumstances it could be dangerous, but nothing like an instant death trap.

author: G7PSK
author_rank: Super Contributor
timestamp: June 11, 2015, 03:24:00 pm
content: It's total power that kills dose not matter if its AC or DC high volts low amps or high amps low volts as long as the power level flowing through your heart is high enough your dead. Its the power through the heart and or lungs/diaphragm that is important the brain and nervous system can sustain quite high power levels, at one time and perhaps still quite high power levels were put through the brain in electro convulsive therapy. The same power levels through the heart would be fatal.

author: c4757p
author_rank: Super Contributor
timestamp: June 11, 2015, 03:34:03 pm
content: Quote from: G7PSK on June 11, 2015, 03:24:00 pmOther posters have already explained in detail why that is wrong.

author: G7PSK
author_rank: Super Contributor
timestamp: June 11, 2015, 08:32:10 pm
content: Well perhaps I should have used the word energy instead of power. The only thing that kills is energy it simply does not mater if its electrical, kinetic or chemical or mechanical if you take crushing into account feed enough energy into a living organism and it comes to the point where it no longer lives.

author: Sigmoid
author_rank: Frequent Contributor
timestamp: June 11, 2015, 08:55:18 pm
content: Quote from: VK3DRB on June 11, 2015, 02:25:08 pm20mAthrough the heartis not the same (not by far) as 20mAthrough the body. 20mA through the heart means your chest opened up, and electrodes affixed to the surface of your beating heart.Quote from: VK3DRB on June 11, 2015, 02:25:08 pmYea, don't try it, but I don't think that's accurate. ESR, DC resistance of the skin, various current paths through and on the body, and all that.Quote from: VK3DRB on June 11, 2015, 02:25:08 pmWell, THAT will kill you. There's a ridiculous amount of energy transported through those. Literally enough to power small towns.

author: LabSpokane
author_rank: Super Contributor
timestamp: June 11, 2015, 11:27:27 pm
content: And the answer is *still* Chuck Norris. Electrons flow because they are afraid Chuck Norris will neutralize them.

author: retrolefty
author_rank: Super Contributor
timestamp: June 11, 2015, 11:47:00 pm
content: I agree with AG6QR, it's the current (at certain near constant value) that causes the damage, the voltage required is a variable that has to overcome the specific resistance and source impedance in a specific condition.Current can kill, voltage it depends.

author: VK3DRB
author_rank: Super Contributor
timestamp: June 12, 2015, 03:39:30 am
content: I believe grabbing hold of AC is safer than DC because of the muscles' response. It is nothing to do with the current through the heart. You can let go of AC easier than DC, even though the RMS values are the same.

author: Tinkerer
author_rank: Frequent Contributor
timestamp: June 12, 2015, 04:44:56 am
content: Lethal values are usually listed in amps(ok mA).Keep in mind that static electricity can have thousands of volts behind it yet we dont have people being electricuted every day because of static. You can have thousands of volts going across your heart but if no oomph in the form of any significant amperage is present, you arnt going to feel anything.Voltage is likened to water pressure and amperage to the amounts. You can have water at extremely high pressure, but if you are only squirting out a few milligrams, you arnt going to have any damage occur. Contrast with this low pressure but a huge amount of water and you can most certainly have problems.

author: rs20
author_rank: Super Contributor
timestamp: June 12, 2015, 05:58:36 am
content: Simple: Any statement or question of the form "is it the amps or the volts that kill you" is a stupid, ill-defined false dichotomy. There are some people here saying "you need at least a fairly fixed current through your heart to kill you", and then others saying that "you need a certain amount of voltage across your skin to kill you". These facts are both true, linked by V=IR, showing what a stupid question it is.However, if you ask "given a particular situation, how do I establish whether it is hazardous or not", that's a proper question, and one that has been answered already in this thread.Quote from: Tinkerer on June 12, 2015, 04:44:56 amWrong, if the potential source can't provide significant amperage, then you will not have thousands of volts across your heart. V=IR geez.

author: Psi
author_rank: Super Contributor
timestamp: June 12, 2015, 06:27:32 am
content: This vid explains it well

author: SteveyG
author_rank: Unknown
timestamp: June 12, 2015, 07:34:35 am
content: Quote from: G7PSK on June 11, 2015, 08:32:10 pmYes this is correct. This is why when we design things like defibrillators, we specify energy as it is the only reliable unit for having a consistent effect on the heart. Power x Time is the important factor, although obviously there are a whole multitude of other ways you can die from electrical contact.Quote from: Tinkerer on June 12, 2015, 04:44:56 amStatic discharge can have huge current associated with it, but the discharge is very short, so the total energy is quite low.

author: amyk
author_rank: Super Contributor
timestamp: June 12, 2015, 12:35:12 pm
content: Quote from: SteveyG on June 12, 2015, 07:34:35 amAgreed. With voltages that can penetrate the skin any significant amount, it's the energy which matters.A static shock which is several tens of kV will produce a very high instantaneous current, but the capacitance is usually tiny so there's not much energy in one.

author: fubar.gr
author_rank: Unknown
timestamp: June 12, 2015, 01:00:50 pm
content: Do the amps or volts kill?The problem with this question is that most of the people who ask it, have minimal understanding of what volts or amps are and their physical significance.And to make things worse, the effects of electrocution depend on many unpredictable and hard to quantify external factors, like source impedance, total stored energy, duration of the electric shock, human body chemistry and whatnot.So the problem is that this question doesn't have a simple this or that answer and the full answer won't be understood by laymen.I think the best advice that can be given is to steer clear from high voltages and you'll be safe.

author: tyguy2
author_rank: Unknown
timestamp: June 12, 2015, 01:54:29 pm
content: After all of this, my friend FINALLY admitted he was wrong.

author: Halcyon
author_rank: Unknown
timestamp: June 13, 2015, 02:39:29 am
content: Quote from: tyguy2 on June 10, 2015, 07:15:56 pmYou can only lead someone to proven, scientific evidence, but you can't make them accept it. I've learnt to not waste my breath with people like that (just accept that probably deep down they know you're correct, yet they'll never bring themselves to say it).Reminds me of a friend of mine who is a self-proclaimed audiophile (more like audiophool). He has tried (unsuccessfully) to convince me that his fairly high-end Bluray player can produce better looking video from his 4GB compressed H.264 movies by using interpolation and extrapolation than VLC media player can using a raw Bluray stream straight off the disc. (Also the same guy tried to convince me that his "high end" AC power cables made his audio system sound better.)