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Besides obviously sticking an output of 5V directly to the heart. Are there areas inside the body where resistance in ohms is so low that a 5V electric potential would be fatal?

I got into an argument about this with my roommate after he made a joke about sticking an lightning apple lightning cable directly up his urethra. I told him that his brilliant idea could cause a nasty shock since internal body resistance is so low. He, however, insisted that the lowest internal body resistance still sits at a few hundred ohms and 5V (5V 2.1A Charger) would not suffice to provide a dangerous current.

Would it be possible for internal resistance in this area to be so low that even 5V or less would be dangerous? Say it took a path up the bladder and through the kidneys and to the heart.

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    \$\begingroup\$ Sounds like medical college grad joke. If you have multimeter, propose him to measure the resistance in his urethra. Not sure where second probe will go though. Depends on the area of medicine he is studying. \$\endgroup\$ – Anonymous Oct 23 '18 at 6:47
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    \$\begingroup\$ Plausible: skeptics.stackexchange.com/questions/39869/… \$\endgroup\$ – Alexander von Wernherr Oct 23 '18 at 6:56
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    \$\begingroup\$ Ha ha. This really made my morning. :-) Since the + and - terminals will be very close together, I doubt that the current will travel all the way to the heart. It might result in a shock or tinkling sensation in the urethra area. \$\endgroup\$ – Peter Karlsen Oct 23 '18 at 7:05
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    \$\begingroup\$ don't do this. I mean, don't stick any part of any electrical appliance up your urethra. stuff like this will a) upset the HNQ again, b) fuel the Darwin Awards and c) have us end up with the obligation to ship devices with new hazard signs depicting prohibited uses noone wants to see. \$\endgroup\$ – dlatikay Oct 23 '18 at 19:34
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    \$\begingroup\$ "5V@2.1A" May not mean what you think it means. If you see it on a wall-wart power supply, then the "5V" part usually means that the supply will try to maintain 5V, and the current will be controlled by whatever is connected to it. The "2.1A" usually means, that if the device tries to take more than 2.1A, then the power supply will fail to live up to its end of the bargain, and something else will happen. There's a range of possible something-elses, which cover the space between the power supply gracefully shutting down at one end, and it belching smoke and fire at the other. \$\endgroup\$ – Solomon Slow Oct 23 '18 at 22:38
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if applied for a long duration electrolysis can cause acid/alkali burns - see warnings about swallowed lithium button cells.

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    \$\begingroup\$ You're right, but the question seems to be more about a charger than battery cells. Surely eating a 5V charger would also lead to some injuries, though. \$\endgroup\$ – dim Oct 23 '18 at 11:51
  • \$\begingroup\$ Lookup videos of button cell batteries inside sausages. This is what kills kids when they swallow them. \$\endgroup\$ – Jeroen3 Oct 23 '18 at 12:08
  • \$\begingroup\$ @dim yeah it's not the same, but a 5V 2A supply is stronger than a CR2032, the voltage is higher and the available current is greater, there is more potential for fatal injury \$\endgroup\$ – Jasen Oct 24 '18 at 8:28
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Except if you proceed with a surgery to apply the 5V directly on the heart, or some other vital organ, it certainly can't be lethal.

The resistance between any two accessible points on your body is either:

  • Rather low, because the two points are very close together, possibly on a wet surface (e.g. the tongue... or the urethra, whatever...). So a significant current goes through, and you can feel it (it could hurt), but it won't kill you because the current will not disturb or harm any vital organ because they aren't in its way.
  • Very high, because the two points are far away from each other, in which case the current will be so low you probably won't even notice.

The NIOSH states "Under dry conditions, the resistance offered by the human body may be as high as 100,000 ohms. Wet or broken skin may drop the body's resistance to 1,000 ohms". "Wet or broken skin" could be the equivalent of what you have on the tongue (urethra?), so at 5V it would give 5mA. Which apparently translates to "perceptible but no muscle reaction".

See also: https://en.wikipedia.org/wiki/Electrical_injury

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  • \$\begingroup\$ '"Wet or broken skin" could be the equivalent of what you have on the tongue (urethra?)' - But the tongue, and the inside of the urethra, aren't covered by any skin at all. It seems dangerous to generalize from "wet or broken skin" to "no skin". \$\endgroup\$ – Tanner Swett Oct 23 '18 at 11:55
  • \$\begingroup\$ @Tanner I assumed "broken skin" means "no skin at that location". I may be wrong, but anyway, if you choose these locations (tongue/urethra), you'll end up in the case where there is no vital organ in the way... Well, now that I think about it, maybe not... If you put one pole on the tongue and the other in the urethra. At that point, I don't know. And I don't want to try. \$\endgroup\$ – dim Oct 23 '18 at 12:29
  • \$\begingroup\$ Would you mind to change the wording of "current takes the path of least resistance" because it's wrong? \$\endgroup\$ – Jasper Oct 23 '18 at 18:46
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    \$\begingroup\$ @Jasper Indeed. But honestly, I don't know how to state "current takes all paths, in 1/R proportion, so the least resistance path will take most of the current, and longer paths will take very little in proportion, because their resistance are magnitudes higher" in an intelligible way without confusing everybody. Feel free to edit if you think of a good way to state that with a few words that don't get in the way of the rest of the statement. \$\endgroup\$ – dim Oct 23 '18 at 18:56
  • \$\begingroup\$ I tried........ \$\endgroup\$ – Jasper Oct 23 '18 at 20:05
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He may feel a localised electric shock, with 5V stimulating sensitive areas. The two electrodes for the 5V supply are both within the cable though, so current will only pass through a very small portion of his urethral area. It certainly will not reach his heart, unless he breaks the cable open and pierces his skin with a connector.

On another note, I have friends who engage in putting things up their urethra. (It's known as "urethral sounds".) Whether adding 5V would cause significantly more pain than the already-painful act of sticking a cable up there, I couldn't say, but simply stuffing something up there is definitely not comfortable. (Which is why they do it, of course.)

The average USB cable is relatively large, compared to the urethral hole. I assume he's planning on cutting the connector off, because that simply would not fit up there without causing damage. Even with the connector cut off though, a cable that size is likely to cause some injury for someone who is not used to this. Also the cut-off end of the cable will be rough and will likely also cause damage - there's a reason that people who do this use medical equipment, which is made of smooth, rounded metal. The risk of infection is therefore also very high.

At best, your friend is in for some serious discomfort. More likely, your friend is on his way to hospital, and thereby to infamy via hospital war story. At worst, Mr Happy may be permanently damaged, and your friend will never pee normally or have sex again.

Not recommended.

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    \$\begingroup\$ TMI \$\endgroup\$ – pipe Oct 23 '18 at 11:55
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    \$\begingroup\$ I learnt something new today :) interesting to see what people do with themselves and how it is called \$\endgroup\$ – Anonymous Oct 23 '18 at 13:03
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    \$\begingroup\$ @pipe You read that the question, saw that it involved the OP's friend sticking a USB cable up their knob, and you still scrolled down to read answers? I'd say you opted in on this information. ;) \$\endgroup\$ – Graham Oct 23 '18 at 13:59
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    \$\begingroup\$ @Anonymous On my side, I could have lived without this information. I can feel pain just by thinking about it. \$\endgroup\$ – dim Oct 23 '18 at 14:00
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    \$\begingroup\$ @Anonymous I doubt you'll need to learn how to administer first aid for something like this. It's not immediately life-threatening. The "viral" advice would be that Rule 34 applies - if you can imagine it, there's porn of it, or at least someone is doing it because they really enjoy it. And based on that, the chances are pretty good that kink groups will be able to give advice on how to do it sensibly and safely. (Whilst some kind of injury is frequently involved in kink, you do want to minimise the risk of accidental injury.) So inform yourself of the risks before doing it. \$\endgroup\$ – Graham Oct 23 '18 at 15:36

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