What kills people, current or voltage? Or something else?

[rgawron]

Some people claim, that voltage is dangerous, not current, some claim otherwise. In my opinion, it's neither voltage nor current but the power. In order to do any damage to the body, some changes in its structure or behavior must be made, to make them, power is needed. Do you agree with that? Why?

While this may look like a trivial topic, opinions are varying, so I'm starting this thread.

[Phaedrus]

Current kills. Period. You have to have enough voltage to overcome your body's resistance, but once that condition is met it is the current that determines lethality.

[rgawron]

Even if the current is huge, but voltage is in uV or nV?

[CM800]

I do, when people keep asking these questions... again and again and again.

Current kills, but you need a voltage to push the current through you.

Licking a car battery would only kill you from lead poisoning or having to tear your tongue out to stretch it all the way across both terminals. While it is capable of supply huge amounts of current, It needs a resistance low enough to allow the voltage to push a lethal amount of current through you. A human body simply has too much resistance.

[AG6QR]

It's not either/or.  Voltage and current aren't independent of one another.  Ohms law says they're related, according to the resistance.  The resistance of skin and body tissue is highly variable, depending on how dry the skin is, how much pressure is applied, where the electricity is applied, etc. The resistance of the salt water inside our tissues is pretty low, compared to the resistance of the dry outer layer of skin.

If you insist on saying it's one or the other, it's more directly related to the current.  We can sustain a shock of thousands of volts when we touch a metal doorknob after walking across dry carpet.  But 50 volts can be fatal if the skin resistance is low.

[rgawron]

So if sufficient voltage and current is needed, then we can agree that it's about power that kills/hurts?

[Phaedrus]

So if sufficient voltage and current is needed, then we can agree that it's about power that kills/hurts?

Nope.

[Whales]

Current kills. Period. You have to have enough voltage to overcome your body's resistance, but once that condition is met it is the current that determines lethality.

That's an approximation of the truth.  If the current is at a fatal level you could also argue the voltage is at a fatal level by re-arranging the equation.

It's better to break down how electricity can kill you by different means.  I only know of a couple:

• Organ failure through communication interruption (eg fibrillating/stopping a heart, causing electrical issues in brain)
• Dissipating lots of power in your cells -> organs cooked or blood poisoning from dead cells (burns)

Communication disruption
I don't know much about this, but it's why AC can be more dangerous than DC.  It's also why certain 'paths' (eg hand to foot vs hand to hand) can be less or more safe/dangerous.  Only tiny amounts of power/current are necessary for this.

Given that human R is decently high in most scenarios you need a reasonably high voltage for a effective amount of current to flow.  Hence the 'fear voltage' saying, which is slightly better than 'fear current' but still misses the complexity of some situations.  It is better advice however to give to an average joe, as most power supplies you can kill yourself on are constant-voltage of some variety.

Cooking
Ie raw watts over time.  In certain situations you are kept in the circuit because you lose control over eg your hands and they grip hard.  In other situations you release immediately.  Some current levels are actually safer than ones below them because they ensure you can't hang on to die    but this is heavily situation dependant.


Overall I prefer not to tell people to fear current, as I've encountered people that think car batteries ("100s of amps")  are more dangerous than ("10A") wall powerpoints.  If anything say voltage is a better way to judge situations simply because it's statistically more likely people will electrocute themselves on a constant-voltage (AC or DC) source than a constant current or more complex one.

Opinions on 'safe voltage' levels vary
Depending on the country and guidelines you will find everything from above 40V is dangerous to above 100V is dangerous.  It really depends on the situation -- if you're sweaty and barefoot on a metal or damp floor, then think a bit more about that 50V AC supply a bit more than normal.  If you're in rubber boots and thinking about what you're doing with your limbs then over 100V constant-voltage supply is probably fine.

When I'm dealing with peers getting into electronics I generally say "please don't play with anything that can deliver over 40V without talking to me".  It's an overly safe threshold BUT I don't want them setting fire to their projects either 

[rgawron]

So if sufficient voltage and current is needed, then we can agree that it's about power that kills/hurts?

Nope.

why?

[suicidaleggroll]

So if sufficient voltage and current is needed, then we can agree that it's about power that kills/hurts?

No, it's the current through your nervous system that matters and can stop your heart.  The voltage that it takes to get there depends on your skin's resistance.  Stab the probes through your skin and the voltage required to get to a lethal current level is much lower.  The lethal current level stays constant, only the voltage (and therefore the power) changes with skin resistance, so it's the current that kills.

[Whales]

Electrical safety is not a one-sentence affair.   Nor is it a one-cause-of-danger affair.

Please always be aware that people in different situations will have different types of electrical hazards to deal with.

Also another point to consider: chemical breakdown of bodily parts to make them more conductive.  At certain voltages/currents/power levels the burning/chemical changes will decrease the effective resistance of a person.  This can be dependant on heat through power or minimum chemical energy required for a reaction through the form of voltage, but only the voltage across the affected area (generally a small proportion of total voltage).

[Electric flower]

Neither voltage or current alone kill you,
It's time while you are exposed to current, but to have current you need some voltage and resistance of something you want to kill.

[DanielS]

So if sufficient voltage and current is needed, then we can agree that it's about power that kills/hurts?

You need enough voltage to pass enough current to disrupt normal heart operation but the voltage required to achieve that depends on how much resistance ends up in the path and the amount of current will also vary from one individual to another along with the specific path through the body.

The required voltage may vary 100:1 depending on circumstances but the share of current passing through the heart is always in the neighborhood of 30mA. So, current is a much more reliable measure of potential lethality: any source capable of delivering at least 10mA with enough voltage to deliver it on-contact is potentially lethal. A 5kV source that can only provide 10mA will cause local burns but is unlikely to be lethal.

It is a bit like working with CRTs: hitting a charged cathode (couple of pF charged at 20-50kV) is more likely to cause injuries from over-reacting to pain and surprise on accidental contact (ex.: dropping and shattering the thing) than the shock itself.

[electr_peter]

What kills people, current or voltage?

Wrong question:

• it neglects that current and voltage are not independent. They are dependant
• Nobody/nothing is killing people. People die because of adverse electricity effects on human body
• it neglects that there are more potential dangers from electricity than "current" and "voltage"

Such question shows complete misunderstanding of electricity. Questioner should consider additional education in this topic.
Answer is not simple. Effects on human body depends on electricity source parameters, human action and condition, environmental conditions, etc.

[Whales]

Answer is not simple. Effects on human body depends on electricity source parameters, human action and condition, environmental conditions, etc.

 

[Mechatrommer]

wrong... its the Will of the God, based on the Law that is written on the Tablet in the beginning of the Time, known or unknown to men. what is known is V = IR, as described by many people above... fwiw.

[rgawron]

No, it's the current through your nervous system that matters and can stop your heart.

IMHO heart's pulse is driven by electrical pulses from cells/tissues that produce those pulses, therefore they have their power. If power from external source is small enough, it will not disturb the signal (enough), therefore will not be lethal/dangerous.

I will present my point of view in a different form: let's say you have a tank of water, a wire is sunk in it and you want to boil the content. In order to do that, you need to supply enough power to the wire, so current * voltage has to be sufficient. Power is needed to perform the action.

I think, this is the same case here.

[c4757p]

Some people claim, that voltage is dangerous, not current, some claim otherwise. In my opinion, it's neither voltage nor current but the power.

IMHO heart's pulse is driven by electrical pulses from cells/tissues that produce those pulses, therefore they have their power. If power from external source is small enough, it will not disturb the signal (enough), therefore will not be lethal/dangerous.

This isn't a matter of opinion. Electricity won't consult you before it kills you.

[radioFlash]

Check out Afrotechmod's video on the subject:

[KM4FER]

Hey everybody, lets do a crowdsource experiment.

Grab your favorite multimeter.
Set it to measure resistance.
Grip one probe between your thumb and forefinger of the left hand, do the same with the other probe in your right hand.
Squeeze hard.
Record the reading.
Lick your fingers where you grip the probes and repeat the measurement.
Record the wet reading.
Report your results back here.

For me:  Dry ~700k,  Wet ~60k.

So what voltage would it take to put 30ma through my body.  Sorry, you can't calculate from these readings since the effect of the current flow will be to change the resistance of my body, just like a tungsten light bulb.

[gilbenl]

That's an approximation of the truth.  If the current is at a fatal level you could also argue the voltage is at a fatal level by re-arranging the equation.

It's better to break down how electricity can kill you by different means.  I only know of a couple:

• Organ failure through communication interruption (eg fibrillating/stopping a heart, doing in a brain)
• Dissipating lots of power in your cells -> organs cooked or blood poisoning from dead cells (burns)

This response is closest to the truth, notwithstanding the response from ElectricFlower. The key component is time and thus power. For example, you could zap 2 "identical" people with 120VAC-One will live, the other one fibrillates and kicks it. The deciding factor is when in the cardiac cycle was the voltage applied. Also, referring to it as "cooking" is a bit misleading. Current lethality is a product of let go threshold. Regardless of how you navigate your way around ohms law, when your muscles experience about 10mA, they clamp and you are now inextricably tied to the source. You'll continue to hang on until your muscle proteins degrade due to the heat. In this sense, you are "cooking," but only because you've increased the time and the energy you're being exposed to. Odd are, however, you were dead long before you were cooked.

60 Hz AC is more dangerous because it more readily elicits reentrant circus movements in the heart, fibrillation and a really bad day.

Interestingly, your brain is generally safe-its 3lbs of fat and water. You will loose consciousness quickly because of excess electrical activity (notice I did not say voltage or current), but generally you'll recover. The most critical neurological consequence is loss of communication b/w your respiratory centers and your diaphragm during this time. Unlike your heart, you need regular input to your diaphragm to breathe. Look up something called "Ondine's Syndrome."

The overwhelming majority of deaths from electrocution are due to ventricular fibrillation and cardiac arrest. Some folks do get horrible burns and ultimately succumb, relatively rare as far as I know. Moral of the story: Amps and volts are virtually irrelevant-Its all about work over time. People can and do die from licking 9V batteries! (Edit due to folks missing the point)

[AG6QR]

I will present my point of view in a different form: let's say you have a tank of water, a wire is sunk in it and you want to boil the content. In order to do that, you need to supply enough power to the wire, so current * voltage has to be sufficient. Power is needed to perform the action.

Actually, no.  To boil water, you've got to supply enough energy, not power.  You can supply a smaller amount of power over a longer time, or a larger amount of power over a shorter time.  It's true that the energy has to be supplied quickly enough to overcome the rate of heat loss to the environment, but that's about the only constraint on power.

But the mechanism of what's needed to boil water doesn't have much implication on what is required to stop the heart.

[helius]

People can and do die from licking 9V batteries!

Bullshit. Please stop spreading urban legends.

[BravoV]

Silly question  , you just can't over generalized only at one factor, make the conclusion just like that without the details.

Its all come down to measurable metrics/quantities in order to answer that completely.

Its like asking if a clean/non polluted water can kill people ? 

Eg :
- Will inhaling water (eg:drowning) kills you ? A drop ? A CC ? A liter ? 5 liter ? 10 liter ?
- Will ingesting water (eg:drinking or injecting it into your vein  ) kills you ? A drop ? A CC ? A liter ? 5 liter ? 10 liter ?

Its stupid right ? Like for example to conclude (or worst to debate) that only inhaling water will kill people. 

This isn't a matter of opinion. Electricity won't consult you before it kills you.

Spotted, another sig worthy quote. 

[suicidaleggroll]

You need enough voltage to pass enough current to disrupt normal heart operation but the voltage required to achieve that depends on how much resistance ends up in the path and the amount of current will also vary from one individual to another along with the specific path through the body.

The required voltage may vary 100:1 depending on circumstances but the share of current passing through the heart is always in the neighborhood of 30mA. So, current is a much more reliable measure of potential lethality: any source capable of delivering at least 10mA with enough voltage to deliver it on-contact is potentially lethal. A 5kV source that can only provide 10mA will cause local burns but is unlikely to be lethal.

It is a bit like working with CRTs: hitting a charged cathode (couple of pF charged at 20-50kV) is more likely to cause injuries from over-reacting to pain and surprise on accidental contact (ex.: dropping and shattering the thing) than the shock itself.

^ This

Think of it this way.  Due to ohm's law, you need all three, you can't separate them.  But what you can do is plot the lethal voltage/power/current required to kill somebody as a function of resistance.  Whether their hands are dry/wet, dirty/clean, in-tact/punctured, all matters.

When you plot it up, you see that the voltage required to kill somebody depends on resistance.  The power required to kill somebody also depends on resistance.  The current required to kill somebody does NOT depend on resistance, it's ~30mA regardless.  That's why we say that it's current that kills you.  Whatever voltage it took to get that 30mA across your heart, is what is required to kill you, and the power is whatever it happens to be as a result.

[c4757p]

What kills people, current or voltage? Or something else?

Something else.

Guns?

Oh wait, guns don't kill people, pe--

People.

It's people.

Stupid ones, usually.

[Mechatrommer]

People can and do die from licking 9V batteries!

Bullshit. Please stop spreading urban legends.

"urban legend" does exist... http://www.dailymail.co.uk/news/article-2950641/Woman-electrocuted-iPhone-dropped-bath-charging-looked-Russian-version-Facebook.html (sad that lady is a waste)

[VK5RC]

The most common mechanism is disruption of the normal orderly contraction of myocardial cells triggered by the electrical depolarisation of the myocardial and specialised conductive tissue.  If at very low levels (V=I. R) no effect occurs,  at high levels (briefly) the heart is 'defibrillated'  and once the external electric source stops the heart will almost invariably return to work.  At intermediate levels some sections of the heart are depolarised others are not leading to a rotating wave of depolarisation,  this causes/is fibrillation.  If this is in the ventricle no blood is pumped,   6 seconds later you pass out,  3mins later your brain is mush.

[mtdoc]

Cigarettes.

[AlfBaz]

V=IR

All three variables inexorably linked.
A high value of V alone wont kill you
A value of R alone wont kill you.
A high value of I alone will...

Doe it really need to be more complicated than this?

[nadona]

Simple. Energy kills people.
Energy = Power x time = V x I x Time
If any one of these is small enough, people don't die.

[AlfBaz]

Simple. Energy kills people.
Energy = Power x time = V x I x Time
If any one of these is small enough, people don't die.

If V=I=0 and time=some arbitrarily large number Energy will still equal 0 but given a large enough time you will still die even though Energy=0, therefor I call bullshit

[tautech]

You die by getting fried.
Warning: Content may offend.

https://www.youtube.com/watch?v=l2hPsNTFQjo&oref=https%3A%2F%2Fwww.youtube.com%2Fwatch%3Fv%3Dl2hPsNTFQjo&has_verified=1

[suicidaleggroll]

Simple. Energy kills people.
Energy = Power x time = V x I x Time
If any one of these is small enough, people don't die.

And if voltage or time are large, you won't necessarily die either.  Small voltage with a small current for a very long time will do nothing, even though the integrated energy could be very large.  It's only if the current is high enough that there's a risk.

[tautech]

If you look at this Wikipedia link the graph shows a combination of Time and Current assuming a AC mains supply.
http://en.wikipedia.org/wiki/Residual-current_device

[SL4P]

You die by getting fried.

Not exactly correct.
It is well recognised that excessive dissipation of 'energy' at the points of electrical contact can in fact char your skin - BEFORE - the permanent / lethal damage is done to your internal organs & metabolism.

You mauy not have any hands, feet or fingers - but you will just have experienced a massive shock before your skin became a high-value resistor in a 'flash' literally.

[EEVblog]

Even if the current is huge, but voltage is in uV or nV?

You cannot get a large current flow through your body when you only have uV or nV applied!
In the simplest terms, the body has a high resistance, and it takes X amount of voltage to get a certain current to flow.
Over a certain current, you will likely die. This is why the earth leakage current breaker in your house is rated in current (usually 20mA or so), and not voltage.
Roughly, under 20mA = safe, over 20mA = dead.

[Stonent]

Check out Afrotechmod's video on the subject:

FTFY

[tautech]

We mustn't overlook Time.

Example
Mains powered electric fence ~ 5000V  @ up to 50 A for 1-3ms.    It won't kill you but you won't come back for more. 

[Kappes Buur]

http://support.fluke.com/educators/Download/Asset/2096653_6003_ENG_D_W.PDF

see Electric shock on page 5

[codeboy2k]

The required voltage may vary 100:1 depending on circumstances but the share of current passing through the heart is always in the neighborhood of 30mA. So, current is a much more reliable measure of potential lethality: any source capable of delivering at least 10mA with enough voltage to deliver it on-contact is potentially lethal. A 5kV source that can only provide 10mA will cause local burns but is unlikely to be lethal.

For the record.. When I was 14 I was making a Jacob's Ladder, and I was using an old oil-burner ignition transformer. I've just done some research and see that some are rated at 20 or 30mA... the one I had was only 10mA.. I remember that. 10kV , 10 mA.

When I was building the Jacob's ladder, I accidentally touched the leads with both hands. I don't know how I came in contact with the wires, but it did throw me backwards about 5 meters into a wall, and I survived. I consider myself lucky, indeed.

In my case, 10 mA was survivable. I also now know that DC tends to throw one away from the source, and AC tends to make one hold on.  But this was an AC transformer, and I did not hold on.

[opty]

V=IR

All three variables inexorably linked.
...
Doe it really need to be more complicated than this?

Just like you say
(plus: time and environmental conditions also matter (as said above).)


It is like on those 'Is BJT voltage or current controlled?' discussions. Flow of electrons is directly responsible for the effects (so it is often chosen as 'the reason') but you won't have current without voltage .... discussion goes on.

[SteveyG]

I also now know that DC tends to throw one away from the source, and AC tends to make one hold on.  But this was an AC transformer, and I did not hold on.

That's not really the case and I wouldn't draw conclusion from that one experience. DC will typically cause a singular continuous muscle contraction and it is purely down to how you come into contact with the supply as to whether you're thrown away or grab more tightly onto the source.

[JohnnyBerg]

I remember my colleges at university. There was a lecture about a striking lightning, and in the adjacent meadow cows died.
Students were shocked about these tests, and rebelled 

[timb]

People can and do die from licking 9V batteries!

Bullshit. Please stop spreading urban legends.

Actually, there is a US Navy fatality from a 9V battery. During a safety course the instructor was having technicians measure their skin resistance with a Simpson multimeter. One guy got the bright idea to jam the sharp probes INTO his hands to get a really good reading. The blood and salty fluids carried the current right through his heart and as a result, stopped it.

There is an actual report of this in Navy Archives, so no urban legend!


Sent from my Smartphone

[jpb]

People can and do die from licking 9V batteries!

Bullshit. Please stop spreading urban legends.

Actually, there is a US Navy fatality from a 9V battery. During a safety course the instructor was having technicians measure their skin resistance with a Simpson multimeter. One guy got the bright idea to jam the sharp probes INTO his hands to get a really good reading. The blood and salty fluids carried the current right through his heart and as a result, stopped it.

There is an actual report of this in Navy Archives, so no urban legend!


Sent from my Smartphone

There was a lot of discussion on the 9V battery story/account a while back on these forums. It is a rather different scenario from licking a 9V battery as you need to have good contact to internal fluids at both ends and even if you touched both electrodes of the battery with your tongue the current would flow through your tongue not your heart.

For similar reasons, unless you're very unlucky you're probably safe with low voltage sources even if you have a cut on your hand.

Conversely, there are some quite unpleasant accounts of the Electric Chair failing to kill people and typically taking 5 minutes or more even when it does.

And at the other extreme, biting on a bit of foil in say a chocolate bar when you have metal fillings can be an unpleasant experience if not lethal unless of course you're driving at the time.

[electr_peter]

let mehdi the great teach us something LOL !!!!


although it appears to be comedy, but i believe he did try to convey that low voltage is not all that harmless. it is funny that there is no real safety video that actually correlates body resistances to lethality ... and the joke is ultimately back on ourselves

I don't like that guy's videos. He obviously knows what he is doing but chooses to play idiot role in front of the camera. All videos are to show some comedy bits and some are obviously rigged. Acting is not even convincing in my opinion. You may like his videos but will probably agree that is not best place to learn about electricity for beginners.

[EEVblog]

im not sure how to comment on this video ... and half a million views !

there is another 1 at over 2million views ... crazy ...

150K more subscribers than me, he's doing something right!

[EEVblog]

I don't like that guy's videos. He obviously knows what he is doing but chooses to play idiot role in front of the camera. All videos are to show some comedy bits and some are obviously rigged. Acting is not even convincing in my opinion. You may like his videos but will probably agree that is not best place to learn about electricity for beginners.

They aren't designed to teach, it's pure entertainment and comedy.

[Wytnucls]

Your video on exploding multimeters must have brought in a few subscribers.

[nadona]

Electrical energy kills people.

[f5r5e5d]

http://www.amazon.com/Electrical-Safety-Low-Voltage-Systems-Massimo/dp/007150818X/ref=sr_1_1?s=books&ie=UTF8&qid=1424314216&sr=1-1

really should be on every EE's shelf - chapter on electrical effects on humans, more on world power line distribution and safety grounding practice

[LabSpokane]

Amps only kill who Chuck Norris hasn't already.

[Stonent]

It's WATTS!

[Shock]

I wonder if anyone has been hurt watching his videos yet. Probing wires dangling in the air and PCBs hanging near the edge of the bench will eventually catch up with him.

[StarFishPrime]

Current.
The flow of charge causes local heating and, at surprisingly low level can interfere with the heart and lungs. The former tends to restart itself though the latter will no if the victim is deeply unconscious.

As a physicist this questions throws up the interesting question of how different models  such p.d. may be appropriate in differing situations and how the term Voltage becomes conflated with potential & potential difference. From a physics viewpoint electrical potential is a property of a point in space (i.e. within a conductor) and potential difference the difference in potential energy 'twixt two points. A charged particle moving between them will experience an energy change.

However from an electronic viewpoint it may be more useful to think of p.d as a force pushing a charge (current). In the absence of friction such as resistance a particle may move indefinitely without energy change.  Thus  a particle beam in a vacuum or electrons in a superconductor represents a current without p.d.

Brushing one’s hair on a dry day may built up a potential of thousands of volts, this is not dangerous as the actual quantity of charge that may be pushed is limited causing a small spark and swearing.

We should really use the term potential difference.

[VK5RC]

Only at massive voltages and currents will electrical heating kill you e.g. lightning, usually it is relatively low levels that particularly cross the heart (both V and I) that precipitate lethal cardiac arrhthmias. Skin is not a bad insulator, but once it is broken/penetrated, the body's salt and water make a not bad conductor!

[Zero999]

People can and do die from licking 9V batteries!

Bullshit. Please stop spreading urban legends.

"urban legend" does exist... http://www.dailymail.co.uk/news/article-2950641/Woman-electrocuted-iPhone-dropped-bath-charging-looked-Russian-version-Facebook.html (sad that lady is a waste)

How does that prove one can die by licking a 9V battery?

It could be a faulty charger leaking too much mains current.

It doesn't even say conclusively the cause of death was electrocution. Li-ion batteries contain some pretty nasty substances and can release hydrofluoric acid under certain circumstances which is a contact poison.

[hli]

Actually, there is a US Navy fatality from a 9V battery. During a safety course the instructor was having technicians measure their skin resistance with a Simpson multimeter. One guy got the bright idea to jam the sharp probes INTO his hands to get a really good reading. The blood and salty fluids carried the current right through his heart and as a result, stopped it.

I had read this several years ago in the Darwin awards: http://www.darwinawards.com/darwin/darwin1999-50.html (and the title is on the spot for this forum :-)
So this should make clear its the current, not the voltage (nor power).

[bugs]

Try to get your hands on the IEC 60479. It is a good indication on what electricity your body can and can not handle.

[Zero999]

Actually, there is a US Navy fatality from a 9V battery. During a safety course the instructor was having technicians measure their skin resistance with a Simpson multimeter. One guy got the bright idea to jam the sharp probes INTO his hands to get a really good reading. The blood and salty fluids carried the current right through his heart and as a result, stopped it.

I had read this several years ago in the Darwin awards: http://www.darwinawards.com/darwin/darwin1999-50.html (and the title is on the spot for this forum :-)
So this should make clear its the current, not the voltage (nor power).

That's been posted before but as of yet it has never been verified as genuine.

It's very unlikely a 9V battery would cause death, even if the resistance of the skin was removed. The internal resistance of the battery itself would've been over 18R on top of the body's internal resistance.

According to the article he tried to measure his internal resistance with a meter. He didn't just connect the battery directly to some metal spikes and push them into his thumbs. The meter would've limited the current to a safe level.

[electr_peter]

Don't underestimate low voltages. If low voltage is coming from low impedance source (impedance level of 9V battery is questionable), it can be very painful and dangerous. There were cases in US where 0.5-1 VAC were felt as very strong painful sensation (rural area with ground-neutral voltage difference and pool near the house).

Marinas/harbours can be deadly to swimmers because of ground problems. While voltage gradient may not be high enough to completely paralyse/kill a person in water, it may be enough to restrict muscle movement and drown a person. Fresh water is more dangerous than salty water.

[free_electron]

falling piano's.  definitely falling piano's.

that, and rampaging elephants.

[0xdeadbeef]

Just in case that nobody mentioned this before, but in most of the cases it's frequency that actually kills people - at least when working with mains.
The (ion based) conduction from the sinoatrial node to the heart muscle can be quite easily affected in certain vulnerable phases (even a punch on the heart can kill you if the timing is right).
It's known that lower frequency in the 50Hz region are especially likely to cause a depolarization that stops the continuous rhythm of excitation/conduction (partly bad luck, as the mains frequencies were defined before this was known).
If a current is running directly through the heart (e.g. during surgery or due to implants), the current needed to stop the heart from beating is actually pretty low.
If the (dry) skin has to penetrated and a lot of tissue, bones etc. is between the current source and the heart, higher currents are needed of course.
BTW: that also the reason why defibrillators measure the ECG to time the depolarization and do make sure they are only used in case of ventricular fibrillation and not if the hearts is either working ok or not at all (as this would be either fatal or pointless).

[oldway]

What kills people, current or voltage? Or something else?

Something else: stupidity, negligence and distraction

[Excavatoree]

falling piano's.  definitely falling piano's.

that, and rampaging elephants.

Those audio stones that improve the flavor, cut and clarity of one's music are just as effective at repelling rampaging elephants.

[helius]

That's been posted before but as of yet it has never been verified as genuine.

It's very unlikely a 9V battery would cause death, even if the resistance of the skin was removed. The internal resistance of the battery itself would've been over 18R on top of the body's internal resistance.

According to the article he tried to measure his internal resistance with a meter. He didn't just connect the battery directly to some metal spikes and push them into his thumbs. The meter would've limited the current to a safe level.

Who's to say it wasn't a megger? 

[mikerj]

Who's to say it wasn't a megger? 

Exactly what I was going to say.  The old meggers could generate around 2.5kv and would give you a very unpleasant shock even on dry skin.

"urban legend" does exist... http://www.dailymail.co.uk/news/article-2950641/Woman-electrocuted-iPhone-dropped-bath-charging-looked-Russian-version-Facebook.html (sad that lady is a waste)

This iPhone was connected to the mains, very probably via a faulty (or Chinese knock off) charger.  She won't have been the only person to have been killed by a faulty phone charger either.

[edy]

I think the OP was trying to say that if POWER kills you or P=VI... Then 1,000,000 V x 1 mA would be equivalent to 100 V x 10 A. Both situations the power is the same = 1000 Watts. Then you could say "1000 Watts can kill you". There is a big problem with this argument. It is not even POWER that kills you... it is POWER x TIME or ENERGY that kills you.

Obviously the 2 situations are not the same as it depends on the resistance since V is related to I by R. You can't just arbitrarily assign the voltage and amperage and say "here hook yourself up to this" and expect V and I to be arbitrary values without knowing the resistance.

The VI relationship given by Ohm's law is V=IR, or V/I = R.

So in the first situation, 1,000,000 V/1mA = 1,000,000,000 ohms resistance would be needed.
In the second situation, 100 V/10 A = 10 ohms resistance would be needed.

Although the "Power" calculation is the same if you put 1,000,000 volts across a 1,000,000,000 ohm, or you put 100 volts across 10 ohm resistance... P=1000 W.... You can't ask if "power" kills you because your body resistance (or the lack of it) in the presence of a high electromotive force or potential (volts) and an unlimited source of electrons (current) is what will kill you.

For example, high voltage alone is not enough. Although the more volts obviously the more amps given a FIXED resistance (according to V=IR). When you get a static shock you could have thousands of volts but because there is a very small source of electrons available it is extremely short in duration. If you had a large reservoir of electrons continuing to flow for a long period of time then yes you would get a considerable amount of energy deposited in your body which would likely burn and boil you.

Similarly, try shorting the ends of a car battery. Yes it is only 12 V but it can deliver a huge amount of current and keep on doing that for a considerable amount of time. The 12 V in a car battery cannot overcome the resistance in your skin, that is why you have very little current going across you. But put a low-resistance device across it (like a screw-driver handle) and watch it spark and glow and get dangerously hot!

So I would say it is neither voltage or current, but BOTH since they are proportionally related by resistance. It is RESISTANCE (lack of it) that kills you in the presence of either a large voltage or current (neither one is independent of the other) and TIME (since power x time = energy which is what is needed to kill you).

[Zero999]

That's been posted before but as of yet it has never been verified as genuine.

It's very unlikely a 9V battery would cause death, even if the resistance of the skin was removed. The internal resistance of the battery itself would've been over 18R on top of the body's internal resistance.

According to the article he tried to measure his internal resistance with a meter. He didn't just connect the battery directly to some metal spikes and push them into his thumbs. The meter would've limited the current to a safe level.

Who's to say it wasn't a megger? 

If it was a megger then it wouldn't be 9V then would it?

And what's the test current used by a megger? Normally it's too low to be lethal, even if it does cause a painful shock, so perhaps the person who did it already had a heart condition?

[G7PSK]

I don't have a Simpson to check but I do have an old AVO 7x. It uses two 4.5 volt cycle lamp batteries in series to give it 9 volts for the 10 Meg ohm range, it only uses a 1.5 volt cell on the lower range's. I measured the current on the 10 Meg range with a Fluke and an Amprobe and a Uni T 61E they gave mw a range of 1.3 to 1.6 m amp feeding straight into the meters shunts (ie) the AVO was effectively seeing a short and delivering the maximum current it could or would. There is no way that you could electrocute yourself with that current unless you applied the probes directly onto the heart itself, which would require opening up the chest. I have read in the past and heard it said that it takes at least 5 mA to kill. The meter that is mentioned in the Navy report is either an insulation tester of the old school variety or some form of bonding tester to deliver a deadly current or the story is just that a story.
As for the AVO to kill some one with it you would do better to batter them around the head with it than try and electrocute them with the probes on the ohm range.

[VK5RC]

There are several, usually congenital, variants of myocardial cell voltage dependant trans-membrane ion channels that lead to easier than usual triggering of arrhythmias.  Eg congenital prolonged QT syndromes,  these can lead to apparently healthy young people 'dropping dead' sometimes precipitated by otherwise trivial stimuli eg exercise (well documented)  and POSSSIBLY a very small electrical insult.
Could the 'sailor'  have had one of these?

[G7PSK]

Interesting articles on electric shocks.

http://www.medwelljournals.com/fulltext/?doi=ijepe.2010.177.181

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2763825/

https://www.physics.ohio-state.edu/~p616/safety/fatal_current.html

And to ensure it is fatal.

http://hypertextbook.com/facts/AprilDunetz.shtml