Is it possible to get electrocuted when live wires fall into the water?
The water container I showed in the video can scale up to a swimming pool, with the finger being a full size body and the distance of the wires also scaled up to match the proportions of the pool.
Of course I didn’t measure the current through my fingers and there are no vital organs in a finger. So let’s play it safe: where I feel the electricity in my finger, you are dead!
You can imagine a pool of water is like a big network of resistors. Depending on where the source is, how far apart the wires are and where the body in the water is, the feel of electricity is different. But here’s some general rules to understand the voltage across the body:
- The maximum voltage across the body is when each wire is on one side of a body and closest to the skin.
- The further apart the wires are, the more voltage there will be across further distances in a pool and can be felt in further distances
- There doesn’t need to be both live and neutral wires in the water to be dangerous. Neutral or earth is already connected through metal plumbing or conductive material or soil on the body of the pool, unless the pool is made of plastic or none conductive material. So the live wire in the water can be even more dangerous as the neutral can anywhere across the swimmer’s body.
- The more chemicals like cleaners or salt there is in the water, the more conductive the water becomes.
Of course the pure water is highly resistive and a body could act like a short circuit in it. That would mean that most of the voltage will go across the water and much less across the body.
On the other hand a much more conductive water will let much more current through and creates more voltage across the body.
AND then there is the issue of the more conductive body part. Like if the water get’s in your mouth, it finds a more conductive path to your flesh. It would make a great complement for the electricity if it could find a hole on the other side to get out of. I’m talking about an open wound that water can get into. Then you will have a real problem.
If the electricity goes through vital organs like heart or brain, they could make real damage or kill. I’ve heard 1mA to 5mA through the heart can cause a cardiac arrest. 110V AC and 1mA current means 110kOhm resistance. It is quite achievable through a highly conductive water. And of course a whole body has a lot of surface to allow current through. Of course that current runs through the entire body and is not focused through the heart. But I think people have died electrocuted in water, so that’s a real danger.
Actually, I really like to know how someone was killed in a pool, like what was the position of the body in relation to exposed wires and water, and what chemicals where in the water. So if you have any stories, please share them in the comments.
And then there is the matter of LED turning on in the water. Isn’t that strange?! Looks like magic, but it has a simple explanation. You know that LED is a diode and unidirectional. But we are dealing with AC here that is bidirectional. This means if the LED doesn’t turn on one way, it will turn on the other way. It just needs high enough voltage across it to turn on, and it is achievable when the water is more conductive.
You see the LED flickers in the video. The reason for that is not the AC frequency, but the bubbles made in the water around the wires, which make momentary open circuits and cause black outs.
And then there is the matter of bubbles. I used to be super in chemistry like 19 years ago. Now I remember nothing! But what is happening is that the electricity is causing the copper of the wire to let go of the wire and become a new molecule. Also there are gasses generated in the process. That explanation couldn’t be any more unclear! So if you know what the actual formula of reaction is, please post it in the comments.
Basic principle is current flow is proportional to the total resistance of the complete circuit. Current equals Voltage divided by resistance. Consider the pool water to be a very large amount of parallel paths of resistance. This results is a very low total circuit resistance. The resultant current in the supply circuit would therefore be quite high, certainly more than 30ma which would trip the RCD in less than 30 milliseconds. RCDs are designed to provide personal protection from current passing through the heart by limiting the current to no more than 30ma for 30 milliseconds.
I love your explanation. Thanks
I’m scared. Thank you for the post
Thank you so much! That is a great way of killing yourself.
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Hi Mr. Mehdi,
Thank you for this video, it is very conclusive at least for me. I was wondering of the “bare wire heating system” and “active vs. passive isolation” used by some manufacturers like this one;
https://www.stiebel-eltron.com/en/home/service/faq/what-heating-systems-are-used-in-instantaneous-water-heaters.html
…in fact I am even using an electric instant heater like this and I am having some thrills knowing that the bare wires from 220 Vac were in direct contact with the water flow.
best regards,
Dorin
I am not sure whether or not anyone commented on this yet but the reaction that takes place when the salt was introduced is called electrolysis. The bubbling that you observe is the water (H2O) separating into O2 and H2 gas.
2H2O -> O2 + 2H2
You forgot about the salt (NaCl) 😛
There are actually quite a lot of different reactions occuring, however, you also should keep in mind that a lot of the bubbles you see being produced are simply dissolved gases coming out of solution as the water is heated by the electric current.
In the salt solution, the main gases produced are H2 and Cl2, NOT O2 (although a bit of O2 is still produced). Also the copper gets eroded through both electrolytic oxidation, and by the chlorine (this forms Cu(OH)2, and CuCl2).
At the cathode, some Na metal does deposit (and instantly reacts with the water to form H2 and NaOH), but mainly the water gets split by 2H2O -> H2 + (OH)2 which forms 2NaOH(aq).
Also, some of the NaOH reacts with the Cl to form NaClO and there will even be a bit of H2O2 that forms!
In the places where an actual arc formed, things get MUCH more complicated with various Nitrogen oxides being produced (and some reacting with either the basic water, or with the copper electrodes, to form nitrate salts), and oxygen also being split to form Ozone as well as various radicals, which can all react with the electrodes as well as any organic material that is in the water.
Hint: voltage is fixed.
Human body is more conductive (lower R) than freshwater, even when it contains chlorine.
V=IxR
As resistence decreases, I (current) increases for a fixed V
With saltwater, the R is much lower than the human body, therefore less current flows through the body and more through the water.
Freshwater is more dangerous with electricity than saltwater.
I love your explanation. Thanks
Hi Mr.Mehdi,
I watched some videos where can make welding machine by use a mixture of water and salt!. Used a piece of copper connected in line and put it in the brine.Also,a piece of aluminium put it in the brine and connected with nutrol.And simply you can welding
Can you explain what happen
Check this;
http://i.imgur.com/Nt7it7k.jpg
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Mehdi I love your videos but you make one big mistake in your thinking could lead to someone getting killed and I hope you correct.
The notion that freshwater is less dangerous is completely untrue. Freshwater could be MUCH more dangerous. The reason is because with a poor conductivity, there’s a larger voltage potential across your body. So especially if you are fully submerging yourself in a body of water for instance, this can become very dangerous. There are multiple instances of people becoming paralyzed or dying almost instantly while I’m freshwater because of this.
You got it backwards. In series resistors, there is higher voltage on higher resistances. Think of it as a voltage divider. Your body has the smallest resistance in pure water. So in series resistors, when the same current runs through water and body, as V = R x I, the voltage over smaller resistor is smaller.
Wouldn’t that mean that more current is allowed to pass through the body with a lower resistance? I don’t know any stories about water electrocutions, but I’ve heard many stories about people who have been injured/killed by lightning which strikes a tree in close proximity… the explanation I hear every time is “The human body provides a low-resistance path for the energy from the strike to travel.” Can you explain why that reasoning works differently for a body in the pool?
Well, it is less likely to get electrocuted in pool, because there is a huge body of water around you which is somewhat conductive due to chemicals to clean it and such. The body resistance is not too high either, but imagine so much water would be like parallel resistors make them smaller and more current will flow through water than body.
In case of lightning, if you are close to a tree, and a tree is very high resistance, the lightening will leave the tree body and go through low resistance human body.
Hello Mehdi
I really enjoy to watch your videos but I have one thing which was a little confusing for me. You said that we can imagine water as a net of resistors. Does it mean the combination of parallel and series connections?
I saw you replied to Cory R about series connection and when you replied to Kubakuba you said about parallel connections.
I am sorry for my poor english.
Yes, it’s a combination of both. Imagine it like the magnetic lines around a magnet. Every line from your finger to the wires is series resistance, and all those are parallel to each other.
No. You got that wrong. In fact you just contradicted yourself.
Nevermind water. Assume a metal car, very low resistance all around (way lower than salt water). While you are in this car a live power line lands on the car. Because the car has very low resistance, the voltage potential across your body as you sit in the car is very small in any direction. So, as you sit in this car which is connected to a live power line you are completely safe from electric problems (if car catches fire, that is a different danger).
Current is what will kill you.
If you are in a conductive pool. The potential difference from any one point in the pool to any other point in the pool is relatively low. So the potential across any of your body parts that are in the water would be relatively low. I = V/R. As V, the voltage DIFFERENCE goes down (i.e., more conductive water) the current through your resistive body also goes down. Less current less danger.
V in your formulas is not a fixed value. V is the voltage DIFFERENCE. It is the Voltage difference that causes current flow. If you take the red lead from a voltmeter and touch it to the positive terminal of a 9v battery the meter will read zero because it has no reference. Now if you touch the black lead also to the positive terminal of the battery, it will still read zero. The meter is reading the difference in voltage potential, and from the same place there is not a voltage potential difference. Only when you move the lead to the negative terminal is there a difference in voltage potential, so the meter will read 9v.
Try this. Get a small pool of mercury. Put one lead from a battery into one end of the pool. Connect the other lead of the battery to a small lamp. Then complete the circuit by running a wire from the lamp to the other side of the mercury pool. If you put your finger into the mercury pool, nothing will flow through you finger. If you put a voltmeter across the two sides of the mercury pool, the voltmeter will read zero volts.*
* In reality, since room temperature mercury is not a superconductor and does have a miniscule amount of resistance, if your voltmeter is sensitive enough, you “may” be able to read micro volts. And yes, therefore, your finger will have pico amps triversing it. But you can also get pico amps from nerve firings if you do something to cause your finger to feel pain.
So I think I know what’s going on in the salt containing solution. I study water oxidation electrocatalysts and i’m quite certain that what’s causing your water to turn color is the dissolution of Cu(II) most likely forming Cu(II) oxide. Cu(II) is an effective water oxidation catalyst, and so you are now able to produce oxygen temporarily during the anodic portion of your current oscillation, hydrogen at the cathodic, and the combined gases, current, heat etc. cause a small fire which is why you can see the tips of your electrodes lighting up.
As for why you don’t see any of this happening without NaCl present I suspect its a lack of charge carrying ions. If Cu dissolves without NaCl, it most likely immediately replates back onto the electrode during the cathodic swing. With NaCl the Cu can dissolve and then the cathodic current can be carried by the NaCl ions instead of replating the Cu.
CuCl2 may be forming but I would expect it to only be a transient species. In water it is a blue salt and your solution is clearly black. This indicates the formation of Copper(II) oxide, CuO. The singly oxidized form of Copper (Cu2O) is a reddish brown color. It may be formed in slight amount but given Copper’s tendency to be in a 2+ oxidation state it’s pretty safe to bet that its CuO thats being made.
I cannot explain why one wire is being eroded more than the other. Oh well can’t win them all.
I’m guessing that is because you have a live wire and a neutral one. So I think the neutral one never properly anodizes because its charge stays at 0V. The live one oscillates, however, so I think that’s why it gets so corroded. Not sure, though.
Voltage is relative though, and the container was non-conductive. So BOTH electrodes undergo electrolyses on BOTH directions of the voltage. With only 2 electrodes, the notion of ‘live’ and ‘neutral’ simply makes no sense.
The water doesn’t “know” which electrode is ‘live’, it just feels the potential difference BETWEEN them.
Why must electricity reach the earth through the lowest resistor? I’m really ignorant of the topic in question, maybe you can enlighten me on this one :).
well imagine you have a bucket of water in a high place with two hoses sticking out, one with smaller diameter and one with larger. The larger diameter shows a smaller resistance against the flow of water and so more water drains that way. In a similar manner, electricity goes more in the path of least resistance. Doesn’t mean there is no current through the higher resistance paths. Hope I answered your question!
Thank you very much. I think I didn’t formulate my question clearly. I actually understand why the current follows the path of lowest resistor but what I don’t understand is how does the current leave the lowest resistor? For example if there is a bucket of water on the ground in which a working electrical device is dropped; how does the current leave my body given that I’m the lowest resistor in this case?
Well I’m more confused now! Just throwing an arrow in the dark here: a circuit need to be closed for the current to flow, which means it leaves the supply, runs through the resistance and returns to the supply. Otherwise there is no current if the circuit is open. Hope that answers your question.
I dont really know how to paint this picture well for you, but i will try. Remember the current is not just trying to flow. The electrons are trying to meet with the opposite parts from the earth. Naturally there is that drive for -ve electrons to meet the +ve to complete the circuit and vice versa (unlike charges attract) as a result current flows. Now the lightening containing Millions of these electrons are trying to meet their pairs on earth (ground) and directed to a tree by the lightening voltage surge. If by any means a less resistive body is close by or in contact with the tree, this less resistive body packs more of the opposite charged and routes to the opposite charge than the tree and hence most the electrons run to the body and then to the earth. thats how it happens in layman terms.
Try this;
Somehow Get a low voltage current to flow through you enough to cause a tingle. Then get on insulated surface or wear a shoe, then touch the bare wall/floor with a finger tip and notice the tingling feeling, increase the finger touch to full and then to two finger touch and the tingle increases (more route for more electrons) hence more electric shock/tinling feeling and so on. I hope i made some sense.
Hmm, I’m surprised that only one wire fell off. This being AC, I’d expect both to be consumed at about the same rate. Although maybe some subtle differences in their geometry combined with differences in positive and negative ion mobility, etc. played a role…
Electrolysis should produce hydrogen, oxygen and chlorine (if you used table salt). Brown precipitate is probably hydrated copper (I) oxide. You may also get some sodium hydroxide, but it’s hard to be sure: there’s a lot going on in the system, and I’m too lazy to do a thorough analysis.
Contrary to what suit said, you never get metallic sodium, not even for an instant: that only happens in anhydrous media, such as molten salts. I also doubt you will get oxygen and hydrogen burn up: while technically possible with active species like H and O in single-atom form, AC frequency is probably too low for that to occur: by the time polarity changes, the gas atoms produced during the previous half-cycle will have recombined into molecular form.
Yeah, it was strange that one wire burnt out. I’m guessing they start at the same rate, but one might fall forward randomly, and that generates a positive feedback (like heating more) that starts consuming that one faster and faster.
Only one wire corroded cos electron flow is in one direction and carries the molecules of electrode A to deposite on Electrode B and impurities dropped off on the foot of B.
The corroded electrode suggest electrons originate from here and terminate in the other. thats the negetive i gues (sorry have lost some mem of my elementary physics and chem)
Remember in AC current there is a slight preferred direction for current to flow.
Thanks,
Scientist Smith
So, here is my story. I was very little and at that time we didn’t had hot water for several days. My mother had to bath me, so she used an old rusty water heater. She put the heater in a bucket and waited to warm the water. The heater itself was 3KW/230 Volts. It looks like that: http://tashev-galving.com/images/items/029%20NPS%20185.jpg
After the water was warm enough she checked the water putting her finger in the bucket. I wasn’t next to here, but there was a big scream coming from the bathroom. I have never heard my mother scream like that. I am an electrical engineer, but still, I will not try to put my finger checking the water if there is something connected.
Cheers
Maybe just the water was too hot! And again, maybe her feet were shorting her body to earth and the electricity passed through her entire body. In my case the electricity would only pass through my finger.
It can be one or both of two things. Either she completed the circuit or she, like Electroboom said became the path to ground.
Thanks,
Scientist Smith
Actually, the electrolysis of salt water tends to produce sodium-hydroxide and chlorine.
As for dropping a hairdryer etc in the bath, the reason this is dangerous is that the plughole connects to a (usually) metallic pipe which is earthed, and the natural reaction is to try to pick up the hairdryer, causing a current path from hairdryer-hand-foot-water-plughole (it’s safer to leave it in the bath, and jump out). BUT, the RCD (residual current devices) are amazingly good at cutting the power now: they use a current transformer to measure the current flowing in both the live and neutral lines, and if this differs by a few mA for a few ms, the power is disconnected. So you’d probably survive.
I agree.
Scientist Smith
There are the old suicide stories with throwing toasters into bathtubs, how does that work?
This is a strange scenario, and of course, I would never do it. But what If I brought an external power source (replicating household power) and a toaster onto a boat, and threw the toaster into the lake. What would happen?
Nothing, unless a fish hooks itself to the wires, in which case you would have a BBQ fix!
I agree and it would be quite cool if it did do something.
Thanks,
Scientist Smith
@Michael – that is not correct 😉
Because its a solution with Salt the solution gets broken up into chlorine and natrium – the chlorine evaporates and makes some of the bubbles
the natrium reacts with the water (this causes the sparks) and forms natriumhydroxide and hydrogen (which also causes bubbles)
additionally the water itself gets separated into hydrogen and oxygen (those also create bubbles)
some of the hydrogen and oxygen instantly get burned up by the exothermic natrium-water-reaction back to water again (with also causes light/sparks)
some of the hydrogen and chlorine does the same and reacts to hydrogen chloride (which also causes more flashes and bubbles)
and then of course the copper dissolves in the water (from the anode) and builds up back at the cathode
the whole process (ignoring the copper thing) is called chloralkali elektrolysis where of course no separation is done and there are all those fancy reactions
in practical application you’ll separate the reaction products and you’ll get chlorine, hydrogen and natrium hydroixide
Aaah, you’re actually generating hydrogen and oxygen there — see http://en.wikipedia.org/wiki/Electrolysis But I guess since you’re using AC you generate both hydrogen and oxygen at the same electrode, and then they burn up again. You don’t want to have large amount of hydrogen floating around in your house…