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While playing with mosquito racket in my home, I unscrewed the racket and touched the 2 wires with my hands. I felt that my bones were dislocated, I got shocked, but I am not dead.

My calculations say that I should die:

the output voltage is 5 kV to 10 kV, my body resistance is approx. 50 kΩ, the current through my body is 0.1 A if 5 kV to 0.2 A if 10 kV.

According to the table at https://www.physics.ohio-state.edu/~p616/safety/fatal_current.html I should die; I tried this many times but I am still alive.

I think my interpretation regarding current, voltage and my body resistance is wrong (if right I would be dead by now) - please tell me why I am not dead?

pankaj prasad
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    Possible duplicate of [How much voltage is "dangerous"?](https://electronics.stackexchange.com/questions/19103/how-much-voltage-is-dangerous) – Dmitry Grigoryev Jun 11 '18 at 08:12
  • Comments are not for extended discussion; this conversation has been [moved to chat](https://chat.stackexchange.com/rooms/78746/discussion-on-question-by-pankaj-prasad-why-am-i-not-dead-after-repeatedly-touch). – Nick Alexeev Jun 11 '18 at 20:19

6 Answers6

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The circuit is not quite as you have described. As stated in the comments (amongst the sea of humor), is that a bug zapper is not an ideal voltage source. It can't deliver very much power, even though the voltage is high.

You can consider the circuit more like this:

schematic

simulate this circuit – Schematic created using CircuitLab

(values are guestimates).

The net result is you will get an initial current spike of maybe a few 10's of milliamps, but only for a few microseconds. After that the bug zapper simply cannot sustain the current, and so the terminal voltage will drop, and the current will most likely end up being less than a milliamp.

It's not the peak current that kills you, but a current sustained long enough to deliver enough energy to kill you.

As to why it kills the bugs, that is simply a case of bugs being smaller than you. It will take far less energy to cook a small bug than it will to stop a human heart.

Tom Carpenter
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    Two continuous miliamps is enough to kill you :) – Long Pham Jun 07 '18 at 15:14
  • @LongPham aye, 2mA was probably a way over guestimate. – Tom Carpenter Jun 07 '18 at 15:16
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    Isn't it also partially an issue of the probes (cathode and anode) being close to one another, hence the current doesn't travel through your body? – Ken - Enough about Monica Jun 07 '18 at 17:06
  • @horsehair yes. – DonQuiKong Jun 07 '18 at 17:26
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    @horsehair Yes, that is also a factor. Current has to pass _through_ a sensitive organ, such as your heart muscles or your diaphragm, for there to be a risk of death. And the source in this case is isolated from e.g. local ground, so even if the OP is touching a good ground with a foot or the other hand, current won't be flowing to there from this source. It can only return to the supply in the zapper so its return path _must_ be very close to the source. – Jamie Hanrahan Jun 07 '18 at 17:28
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    @JamieHanrahan you are right about the current path for an ''immediate death''. To add up a bit on your comment, some of the electric death toll occurs a long time after the actual shock because of burn related complications. In all honesty, it is a gruesome way to die in both cases – Simon Marcoux Jun 07 '18 at 19:50
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    I'd argue that the proximity of cathode and anode is much more relevant to the question than the current. I've touched mains voltage (120VAC @ 60Hz, US) several times -- but I had contact with hot and neutral both with a single hand, so the current primarily dumped through my hand instead of traversing my body. Hurt like hell, but since I had contact with the source before it was energized, I didn't even get burned. My hand was numb for a while after one particularly unpleasant jolt... but still here typing :) – Doktor J Jun 07 '18 at 20:44
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    @LongPham 2mA is not fatal. [IEC 60479-1 suggests](https://en.wikipedia.org/wiki/Electrical_injury#Lethality) that you need at least 30mA continuous to produce a measurable (up to 5%) risk of ventricular fibrilation. This is why GFI or RCD devices typically cut in at 30mA. The same chart rates up to 5mA as "perceptible but no muscle reaction" (AC-2 region) for indefinite exposure, and for contrast, up to almost 500mA equally falls into that category for exposures <10ms. – J... Jun 08 '18 at 16:56
  • @J... My information came from a project designing a bio-impedance analyzer. – Long Pham Jun 09 '18 at 13:39
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    @DoktorJ I've personally had 240V mains (UK) across my body (one hand on live, the other on neutral). I think the only reason I live to tell the tale is the resulting muscle spasm disconnected one wire from my fingers, limiting the time I was cooking for to only a fraction of a second, meaning insufficient energy to kill me. Still, couldn't walk in a straight line for about 10 minutes. – Tom Carpenter Jun 10 '18 at 09:33
  • Isolation which @JamieHanrahan mentioned should probably be part of the answer. – R.. GitHub STOP HELPING ICE Jun 10 '18 at 17:09
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  • Passing the current through a finger is relatively safe, as there is not enough current to burn you, and it's far from your heart.

  • Passing the current from hand to hand puts the heart somewhere "in the middle" of the path, but clearly not in direct series. Plus your skin can still present a large resistance.

  • If you pass the current across your chest, the chance of death is higher.

  • If you had probes that went deep into your chest, and passed the current through the probes, you'd dramatically increase the risk.

As others have stated: The bug zapper has a very limited amount of power that it can deliver. There is enough energy to fibrillate a bare heart, but yours is protected in your body.

Bort
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  • Isn't your skin surface resistance also much lower due to humidity? This would lead the current just over your skin, and not through your body. – chthon Jun 08 '18 at 13:18
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    @chthon: There are several layers that make up your skin, and they have different electrical properties. I seem to vaguely recall that the dermis has much smaller resistance, possibly due to all the blood vessels and whatnot. (Which is why touching say a 9V battery with your finger does not hurt, but if you stick needles deep into your skin, and connect the battery to those, it hurts like heck. Don't ask me how I know.) – Nominal Animal Jun 08 '18 at 13:45
  • @NominalAnimal There's a story going around about a guy who stuck two probes in each of the thumbs and did in fact die from it. Perhaps you were lucky. Was a 9volt powered multimeter I believe. – htmlcoderexe Jun 12 '18 at 07:34
  • @htmlcoderexe - The key to that story is that the probes were *in* his thumbs, as in his blood. Regardless of the legitimacy of that story: OP, I'm assuming, did not have a direct path to their innards with the zapper. – Bort Jun 12 '18 at 11:19
  • @Bort I guess it depends on just how deep is "deep into your skin" for Nominal Animal's case specifically. For OP, that was obviously not the case. – htmlcoderexe Jun 12 '18 at 11:22
  • @htmlcoderexe: Not even I am (nor were, as a child) dumb enough to do it across my heart (i.e. one needle on one side of the body, the other on the other side)! And I was not talking about sticking them into ones flesh, just deep enough to reach the dermis, not even the fatty tissues (so say 1-2mm or so, depending on body part and person), as skin thickness varies. [Electrical muscle stimulation](https://en.wikipedia.org/wiki/Electrical_muscle_stimulation) is a known working thing, and 9V is definitely enough to disrupt ones heart. Also, to do damage in dermis, if the path is short enough. – Nominal Animal Jun 12 '18 at 11:54
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To put this more like an electrical engineer would put it: this high-voltage source has a high internal resistance, and understanding what that means answers your question.

Marcus Müller
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  • I don't think "internal resistance" is a term hard to understand if you google for it, to be completely honest :) – Marcus Müller Jun 07 '18 at 20:29
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    @MarcusMüller You might just want to elaborate a bit upon it (thus making the answer more self-contained), since this answer just seems so small. :) – EKons Jun 07 '18 at 20:30
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    Nope, I think the main *strength* of this answer is is shortness. I could re-explain internal resistance, but I'd do that worse than wikipedia or a million other sources. I honestly, not out of laziness, refuse to reproduce "common knowledge" that can be found easily enough – for quality reasons. – Marcus Müller Jun 07 '18 at 20:30
  • a great answer, but IMVHO requiring one correction: **this** high-voltage source, not *the* high-voltage source... there definitely *are* high-voltage sources with internal resistance low enough to kill a human (e.g. lightning, HV lines, any high-power source in general) –  Jun 10 '18 at 01:16
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    I find this answer fairly unhelpful. If you prefer not to explain the answer fully, then it could be improved by at least including links to sources where the OP can learn the topics he needs to be able to understand it. Doing so takes care of your concern that you will not do as good a job at explaining it as those sources. If all Stack Exchange answers consisted of "You will know the answer once you learn topics X and Y" then the site would be useless. – JBentley Jun 10 '18 at 18:28
  • @JBentley I think I understand what you're telling me, but I had actually typed out a much longer answer, deleted that and then just submitted the first two sentences. Why? Because OP asks to *understand*. From all we know about OP, he's studying electronics. So, he really has the literature and just needs to know the concepts he'd need to look into. For all the others: Really, I don't think googling "internal resistance" is an obstacle any reader of this site would deem to high. And again, I'm no better than wikipedia etc at explaining stuff. *The strength of this answer is its shortness*! – Marcus Müller Jun 10 '18 at 18:38
  • @MarcusMüller I think you misunderstand me. I'm not saying go and edit the answer and put in the explanations. I'm saying provide the links to Wikipedia or whatever source you think explains the topics at the required level for the OP (and future readers) to get the understanding they need. *As I already said*, this takes care of your concern that you will not be as good at explaining it. Without that, your answer boils down to "google it" which is not particularly helpful and leaves the question essentially unanswered. – JBentley Jun 10 '18 at 19:43
  • @JBentley I still respectfully disagree, because I didn't say "google it", but "research the topic *internal resistance*. I know this is kind of unsatisfactory for you, but I'll keep it that way, my apologies. – Marcus Müller Jun 10 '18 at 19:57
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It is not only current and voltage that matter, but duration. 10kV at 1A for a microsecond is about 10 microjoules. You might feel a shock, but it is not enough to actually tense all your heart muscles into paralysis long enough to make you unconscious, or even cause physical damage from heating or muscle contraction.

On the other hand, IF you have a bad heart it might be enough to upset the rhythm and send you heart into fibrillation, which can be fatal. Maybe you are just lucky

Dirk Bruere
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    What energy (in Joules) would be enough to cause any damage to heart / death? – Marki555 Jun 07 '18 at 20:25
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    @Marki555 - Energy is not normally a consideration. For instance, back in the 60s there was a case of a patient in a hospital with a wall-powered pacemaker. Unfortunately, the unit was not properly isolated, and when the patient touched the (grounded) bed frame, the (estimated) 47 uA which was applied directly to his heart did the job. – WhatRoughBeast Jun 08 '18 at 00:44
  • @Marki555 No idea, but medical defilrillators can run into the hundreds of joules. Again, duration is the key – Dirk Bruere Jun 08 '18 at 07:25
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Death from electrocution occurs mainly in two situations and is not directly correlated with the actual current/voltage values:

1) Enough current and energy passed through your body to actually burn you inside out 2) A voltage passed through your heart and put you into a fibrillation state.

Both can come into play at the same time!

The first is mainly caused by excessive current into your body. Once the skin is penetrated, it is easy to pass a surprisingly high current into your body. This is why wet + electricity is so bad. It reduce drastically your skin resistance.

Before venturing into the 2nd part, you need also to understand that electricity will have an entry point and an exit point. You can often see a burnt mark at those points when it occurs (in hard situation).

Directly related to that: if the current pass through your heart with a voltage high enough or with some weird frequency, it can put your heart into fibrillation: desync it. When this occurs, you need to reset your heart using a defibrillator like in all poorly written medical drama. A shock does not so much when the heart is flat-lining, but help fibrillation cases.

As for your question, you didn't die because the current entered finger and exited through your finger. It didn't pass through your heart. Also, the current in play we're not enough to cause any significant burns. Specific injuries prediction is on a case by case basis.

In a nutshell, your heart either fail or you burn to death when you die from an electric shock...you might also survive and be severely burnt or maimed by the aftermath. Losing limb is unfortunately not so uncommon.

If you want to know more, the wikipedia article is well written.

Simon Marcoux
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    You missed one: 3) Enough current passed through your diaphragm to prevent you from breathing effectively, for long enough for you to suffocate. It takes less current to paralyze the diaphragm (or paralyze it "enough") than it does to induce fibrillation, but of course this route takes longer to have a lethal effect. – Jamie Hanrahan Jun 16 '18 at 03:55
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    I shivered at how painful it must be to die like this. You are off course right that I missed this one @JamieHanrahan – Simon Marcoux Jun 16 '18 at 04:02
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    And damned frustrating, since you'd be conscious for part of it - but, depending on the path the current is taking, unable to move to fix the problem. Shivering indeed. – Jamie Hanrahan Jun 16 '18 at 06:19
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    There is a table in this page: https://www.allaboutcircuits.com/textbook/direct-current/chpt-3/ohms-law-again/ that shows current levels for various detectable and deleterious effects, broken down by male vs. female and for DC vs 60 Hz AC vs 10 kHz AC. – Jamie Hanrahan Jun 16 '18 at 09:05
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Another aspect to consider is frequency. Mosquito zappers are DC, but they don't supply constant DC. After the voltage is stepped up from 3-6 VDC from the batteries through a voltage multiplier, it comes out in rapid pulses. As soon as voltage is applied and your body begins to take the energy, the current is stopped. I don't know exactly at what frequency mosquito zappers operate, but at high enough frequencies, the human body can simply absorb the shock in the skin before it reaches deeper into the nervous system and your heart. That's why you're able to be shocked by a tesla coil without dying. You still feel it, but it doesn't penetrate far before the pulse ends and simply dissipates before the next pulse comes along.

Ed Bruce
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