How many volts of electricity would it take to kill someone?
Kieran Jones from Swansea (Age: 5-14)
Filed under: age 5-14, Derek Wood's Big Answers, Electronics Big Questions, Gavin Brown's Big Answers, Lisa-Marie Martin's Big Answers, Mark Dowsett's Big Answers, Physics Big Questions |
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It’s not volts that kill it’s the Amps…. you only need 50mA across your heart to kill you, there is enough in a 9v battery to kill you under the right conditions.
Voltage just pushes the current through you, the higher the voltage the easier the path through your body, it all depends upon your resistance, if you touch a 9v battery with your dry finger you won’t feel anything, if you wet your finger and try again you will get a current flow and you will feel it tingle. (don’t try this at home) (especially if you have a pace maker)
Kieran, it’s not the volts that kill but the current. When I was a boy 60 years ago my physics teacher made me stand on a large block of paraffin wax while he charged me up with static electricity from a Wimshurst machine to 100,000 volts. I then had to shake hands with a friend standing on the floor. We both got a shock that tingled but I didn’t eat chewing-gum in physics lessons any more. Of course, he couldn’t do that today!
It’s the amount of current, the amps, that the volts can push through your body that can do the killing. That depends on the resistance of the body, how dry everything is and how health you are. If you are fit, your hands are dry and you are wearing leather-soled shoes then it is unlikely that you would feel 50 volts. However, if both hands were wet and you connected 50 volts across them then you might get a nasty sensation that could upset someone with a weak heart.
The worst situation is when the electrical connections to your body push the current through your heart – such as from hand to hand. That is why electricians who might come into contact with a high voltage work with one hand in their pocket and wear rubber-soled shoes. This is also why the safest thing to do if you are caught outside in a thunder-storm is to crouch down while standing on one foot – but that’s another story.
It is not the voltage which kills you, it is the current. For example, if you get a shock from static electricity, the voltage involved can be in the millions of Volts range (mega-Volts), but the momentary current is millionths of Amperes (micro-Amps). Makes you jump, but that’s all. On the other hand, the 240 volts AC of the domestic mains supply can easily kill under the wrong circumstances, for example when the skin is damp.
The voltage drives the current through the body, but it cannot drive more current than is available from the source, and a certain minimum voltage is needed to get the current through the barrier of the skin. The epidermis (dead skin at the surface) is quite a good insulator, and around 50 V DC or 30 V AC is required in order to feel the effects when the skin is dry. Also, the skin can limit the current from higher voltages. However, because the skin contains a lot of salt, and salt solution is a good conductor, wet skin “allows” electrical current into the body more easily.
Depending on the route that it takes through the body, a current in the range 10 thousandths of an Amp (10 milli-Amps) can kill by interferring with the rhthym of the heart. Larger currents burn along their tracks, and can kill by damaging organs and the nervous system.
So, pretty unpredicatable. Any source that can deliver more than a few 10s of milli-Amps or so at a voltage of a few 10s Volts, should be considered as dangerous.
Only 50mA is enough to kill a person, but also other factors have an influence on the result. a persons physical makeup such as size, physical condition, age, state of health etc, all have a bearing on the outcome to contact with electricity, In addition,environmental conditions are important in influencing how easily the current will pass through the body and the severity of the contact. If a person is stood on a wet floor in bare feet, the path to earth is easier and the effect worse than in dry conditions wearing rubber boots.
9.572 volts in a single battery has the potential energy to kill you through a regular conductor. However you need to be smaller for this to happen.
Sam from Science St Georges School
Hi Kieran,
It is not the actual voltage that kills you but a source of voltage high enough to cause sufficient current flow through the bodies muscle and hairs. As everyones body is different a definite figure can not be given, however, it is possible that as little as 1mA of current can be felt by the body.
I was told this by my father:
It’s not volts that kill you, neither is it current (amps). It’s energy measured in joules. 1 joule is 1 amp at 1 volt for one second. It takes about 200 joules to deliver a fatal shock.
Curiously, the figure of about 200 joules works for just about any execution. A speeding bullet has around 200 joules. a falling guillotine has about 200 joules. Strangulation takes about the same as well. The most energy efficient method is poison.
its the currant that will kill you and yes theres enough currant in a car battery to kill you it only take 50 mA to kill someone and as far as what bob lerwill said he obviosly doesnt know what hes talking about becaus Amps are measured in Joules there not separate
it is correct to state that it is the energy produced by electrical dissipation that kills, rather than the current itself, but your father should have gone a step further in emphasising that it is dE/dt that kills — which is why he referenced “for one second” — not E itself. for this reason, 1A at 1V for 200s, while still producing 200J of energy, would not be harmful in the slightest. the mechanism proceeds through the rapid accelerations of and collisions between the charges that constitute the current (driven, as others have said, by the voltage differential across the circuit). as the particles collide, there are inelastic momentum transfers that manifest by a conversion of electrical energy to heat energy.
i believe your father is a bit mistaken regarding the amount of energy supposed sufficient for various methods of execution. 200J is far, far too low for a rifle-fired bullet of any caliber…i should think the correct figure to be at *least* a magnitude greater, and probably closer to the 5MJ-range…and a guillotine of 10kg at 2m also has about 2kJ, or one magnitude greater energy.
furthermore, it is the *thermal dissipation* that generally kills, not the upsetting of the electrical rhythms of the heart (except in cases of existing victim cardiopathy, usually in the extreme); recall that a heart that has ceased electrical function can be resuscitated by the application of a nominal voltage. it is essential to note that, 1A at 200VDC for 1s, while producing 200J of energy, does not dissipate 200J of thermal energy, so we cannot say how much energy is actually *doing* the killing.
i meant 5kJ, not “5MJ,” obviously!
look its not the amps or voltage the both of them could be 1 each and you could still kill yourself its how long the shock lasts for
Hi Kieran,
First of all, lets think about the question itself.
How many “volts” of electriciity would it take to kill someone?
The first thing we need to understand here is that there is no such thing as “volts” of electriciity.
Voltage is like the “pressure” in a water pipe when the tap is turned OFF. – No water flows = “no electricity”
(you can “feel” the pressure if you stick your thumb over the end of the tap and turn it on. … it tries to push your thumb away, BUT, if you press HARD enough , no water comes out = that is you are “resisting” the flow of water, which is the same as a “high resistance” in electrical terms, stopping an electric “current” from flowing)
Now…
IF the tap is turned OFF, we have LOTS of pressure (voltage) but NO water flow in the pipe feeding the tap)
When you turn the tap on, the water starts to flow in the pipe. – and this is the “same” as electrical “current” flowing in a wire, or through a “body”
NOW,
Lets use these “ideas” with “electricity.
So, you take say a small battery, say a pp3 “9volt” battery.
The PRESSURE is the 9 VOLTS of electrical “pressure” that exists across the battery terminals,
BUT
IF nothing is connected to the battery, NO “Water” , that is electrical “CURRENT” can “flow” becuase although the “pressure” or voltage is “there”, there is nowhere for the “flow ” to go, UNLESS you make a path for it across the terminals, ……. SO ….. WHAT IF ….
You stick your finger across the terminals .?
So..
There is 9volts of electrical “pressure” trying to “push” an electrical current (“flow”) through your finger.
BUT, 9 volts isn’t a great deal of pressure, and your finger *isn’t very good at “letting” current flow through it.
(* isn’t very good = electrical “resistance” )
(or impedance for the purists, where alternating current is present)
So, … to get “electricity to flow through your finger” …
(don;t worry, we’ll get to the nasty killing bit in a moment!)
We can either raise the pressure, that is get a “higher voltage” battery to “push” more current through your finger, OR, ……we can *”make it more easy” for the current to flow through your finger ….. and that can be done quite easily by making your skin wet ….
(* make it more easy = lower electrical “resistance” )
(Which is WHY electrical wiring regulations are ttough in bathrooms and kitchens where water is about …)
So, for someone to receive a “fatal” electrical shock, all that needs to happen is for electricity to “flow” in the right amount, across sensitive areas of the body like the heart, or brain. ….. and THAT amount isn’t big,
THATS why earth leakage trips in your house are designed to trip typically at 30 /1000th’s of an amp (30mA) .
Quite a small current ….. but 30/1000 th’s of an amp HURTS …. trust me !!
(and that’s why someone else mentioned earlier about keeping one hand in your pocket …… If you’re going to get a shock …. get it across a couple of fingers, NOT across your arms, which means the current flows through your heart)
And so …. If you happened to be in the bath say, with lots of your skin in contact with water, that is ,,, lots of places for the electrical current to flow into you ….. then … if you happend to touch something live, then not many “volts” would be needed to make a substantial current flow “through you”, but …..
on the other hand, IF you were standing on relatively dry ground, with rubber / plastic shoes on, and you happend to touch a live wire in a light socket say, then …..
although, in a normal house with a mains supply of 240 Volts , that would “normally” quite easily “push” a current through “you” to the ground and give you a nasty shock …,
it’s quite likely you would not actually feel anything at all, becuase there is nowhere for the current to flow becuase it cant “get” through your rubber /plastic” shoes to the ground,
And so ….
To sum up…
It;s the VOLTS that JOLTS, and the MIL’s that KILLS !
Mils = milliamps (milliamp = 1/1000th of an Amp)
Factors to consider. Conditions (humidity would reduce the current needed). Clothing (rubber soled shoes etc.) Amount of current. Path of current through body. Frequency. Length of time exposed.
10 to 15 milliamps = muscular spasms.
15 to 30 milliamps = breathing may stop, heart tremors.
30 milliamps + = Ventricular fibrilation of heart and death.
Under normal conditions it is stated that dangerous levels are 30milliamps for 240 milliseconds.
As for voltage, what the other guys said, it wont kill you.
Voltage = Current x Resistance so it is dependant on the casualty’s resistance at the time. (Higher voltage would be needed to affect someone with a higher resistance).
volts dont kill and a amp and joule arnt the same thing and a joule isnt a volt everysecond a coloumb is what joule per second is measured with. and most things in ur house can kill you.
peace
ok i understand all that. it is the current and voltage needed depending on resistance, flow etc.
a senario i cant get to grips with is this..
lets use d.c. current and the heart/ vital organ path isolated by means of a lab set up. i want to just consider the pain felt by the test volunteer! the test would involve a voltage current rating not to cause too much dangerous heatin through perhaps an arm from elbow to wrist.
first test is carried out with an electronic current limiter set at 10 ma. the voltage set to thousends of volts. such an amount as still to produce a high amout of watts. (10,50, 1000?) anyway this would produce a lot of heat at just a few ma. this is where i am thinking that the overall power could kill. the second test would involve just enough voltage to push 50ma through the arm. the second test would produce much less ‘power-watts’ but acording to servovos is is the current that does the damage. well anyone any ideas about this!
it takes 1/8th of an amp to kill you if it makes direct contact with your skin, 50 ma across the heart, and 1ma to the brain when it is not receiving energy (which is never, so more like 20ma to the brain) Volts would do very little to you. this is why you see people survive lightning strikes, because lightning has low amperage.
Just to add to the debate, i had a medical procedure called dc cardioversion, this was because i had atrial fibrillation or otherwise know as an irregular heart beat, i had two patches attached to me, one on my chest and one on my back, i then had 1 200 joule shock applied to restart my heart and put it back into normal/sinus rhythm, so a 200 joule shock does not always kill and can actually be beneficial!
I am using a 12 volt (2 Ampere max.) ac/dc adapter to treat my “sweaty palms”.
See sample Youtube video – http://www.youtube.com/watch?v=Cc0pj2tf6_4
I only feel a mild jolt when I pull my hand out of the electrolyte solution. But when I switch the polarity I get a stronger jolt both when I put my hands and pull them out of the solution.
Is this safe?
Is it safe to connect two ac/dc adapter in series to get a higher output???
Lightning has very high voltage and very high current. Voltage in the hundreds of thousands of volts and tens of thousands of amperes. The reasons “some” people live is that it takes various paths to reach ground. Sometimes, exiting the body and bypassing vital organs. But, it is “lethal” !!!
Also, the Voltage must be high enough to drive a sufficient current through any device. Ohm’s law prevails. It simply states that Current equals Voltge divided by resistance. However, the source current has limiting factors, therefore not every “source” is fatal ! If a source “capable” of high current (like a house main) flows through a body with low resistance (wet etc.) and this is past vital organs (in the case of hand to hand through the heart)then a fatal current can result !
As many of the other posts point out, volts is not the problemit is amps. To further clarify, Joules a term common used in AEDs measures the watt second delivered. A 9 volt battery is capable of delivering 200 joules, the most common quantity delivered by an AED. When defibrilating to stop the heart with an AED approximately 4% of the energy actually reaches the heart. A common misnomer is that an AED jump starts the heart. It is important to understand that the shock stops the heart in the hope that it restarts and works correctly. So somewhere around 10 joules will stop the heart if given fast enough and to the correct location.
The AMP mA is what kills. My science teacher was a freaking genius with enough projects showing the deadly abilities of electricity so I’ll take his word.
Your science teacher was a genius, but you should have learned exactly what he was talking about (before you quote him).
It’s the “current” through the body that kills you…it is measured in; Amps, Milliamps, or Microamps. The term “Amp ma” has no relevance, except to show your lack of the subject matter…You may have had a good teacher, but you learned nothing.
At first, I thought that the question was for the “theory only”, but after seeing the “sweaty palms” video, I see why people are asking.
People…Please don’t use an A.C. adapter connected to leads attached to your hands. Usually the A.C. adapters that are on the market are made cheaply. If one of them fails, you could be putting potentially dangerous “lethal” current through your heart!!!
If you have; “sweaty palms” or Sweaty Hands”, deal with it. Sweat has a function, to remove excessive heat Etc. in the body. If you feel the need, seek professional help !
Don’t chance being killed !
I keep reading of MilliAmps and danger here and there, but it happened to me to touch with my hands the positive and negative terminals of a welding machine with a voltage of 80 Volts and a courrent of 120 Amps. It was nasty but here I am! Can you explain this to me?
Thanks
Frank
I find the last comment interesting. I almost touched the ends of a charger/starter in a regular AC outlet that was set to 74 amps. I am guessing this would have the voltage down to around 24 volts..? What would likely been the outcome of this?
first i have to say because i am tired of the redudentcy of how many mA it takes to kill you. 65 mA (or 0.065 Amps) at 30 volts will stop the heart of an average human being. And to answer Frank Mascagni i have been doing tests on human conductivity and have found that people who are exposed to above average(but not too high above) amount of electrcity some how act as a circut rather than an area of discharge
The typical resistance of a human from fingers to toe is about 500 oms on an average human (this is with no shoes on). Now with a 120 volt AC outlet you can easily produce 3000V with a nice transformer…This amount of voltage can run 6 amperes through a human. If only if only 0.05A stops the heart you can see how 6A can fry a person.
see:
http://www.allaboutcircuits.com/vol_1/chpt_3/4.html
I have read in newspapers/TV/youtube about a man from India who can wrap himself in wires and let current pass through them w/o any visible damage to him. He makes omlettes on a hot plate kept on his palms and lets the current flow through him. Can any one explain the same scientifically? In the Ohm’s law equation, is he able to adjust his body resistance? Does it mean he has abnormal powers of resistance?
what voltage and current do they use in an electric chair to execute a prisoner on death row?
Would using a 9 volt battery to create an electromagnet harm a small (4 foot 10) person if it were grabbed?
Lots of excellent answers, just not necessarily to the question asked, and I’m sure Kieran has moved on to bigger and better things, but here we go.
First establish a couple of things. As many have said, amps is wot kills, and it’s generally accepted that anything above the ‘let go threshold’ could, possibly be lethal. Not sure of all the figures, but OSHA put that at 16mA. Second, the average resistance of the body? Someone quoted 500 ohms, and the numbers vary, but for the sake of argument, let’s fix it at 1000ohms. Job done! You have 2/3 of the equation
V=I X R
V= 16/1000 X1000
So 16 volts could kill you given the minimum current .
If you wnt to take the accepted killer range of 100-200mA
V= 100/1000 X 1000 = 100V
Before I go, just to back up the A versus V argument. I’ve had 240V (domestic) – bloody nasty experience!
I’ve had 20,00V (ish) – messing around with a car sparkplug on a damp day – it wakes you up at 05.30 when you’re trying to get to work.
And I’ve had somewhere around 1,000,000V – static discharge.
Cheers peeps
maybe it is the amout of voltage that makes amps kill ??
Actually, it’s not the volts that kills,the volts gives that vibrating sensation which can throw one away,while it takes as little as 7milliamp connected across the heart to kill a human being,there is this analogy that someone gave about a tap,but i also want to give a scenario.if water is flowing through a pipe,the water coming out represents the current,the pressure of the water represents the voltage,while the pipe represents the power in watt,current needs a certain magnitude to break the resistance of the skin before it can cause damage.if it was for a source to produce 10000volt with a current of 1000mA,it will not be enough to start a reaction,hence will have no effect on one.
As an electrical engineer, 1st year teachings instruct on how dangerous electricity is, you can feel 9 milliamps, 14 milliamps will cause muscular contraction and 21 milliamps will kill you. This is of course entirely dependant on the health of the individual, whether or not they are sweating/wet or dry, as the body’s resistance will alter. Volts are needed to force the current through a resistance (basic ohms law), Tasers and insulation testers etc, that use high voltages have current limiting devices fitted to make them less harmfull.