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I'm trying to figure out what effects would this have on hand. Let's assume that we touch contacts of said capacitor with thumb and index finger of the same (dry and pretty clean) hand (but I'm also interested what would happen for other combination of fingers if it differs significantly). From what I know about supercapacitors, resulting "circuit" will have the following characteristics:

  • It won't last for long thanks to supercapacitor's ability to discharge very quickly
  • As a consequence of above, it will also have very high current
  • Voltage will drop as capacitor gets discharged

As for capacitance of supercapacitor, let's say that it's 1 kilofarad (perhaps it's an entire battery of them connected in parallel?), which is quite a lot. It also was charged at 1 kilovolt.

I've tried to look up relevant information about this, but almost all sources talk mostly, if not only, about dangers of AC current going through heart, which is a most common scenario in practice but totally inapplicable in my case where DC current goes only through small part of body. Those that talk about other effects of electricity on human body, mention the following additional dangers:

  • heating
  • electrolysis

I've probably missed some here since, as I said, this seems rather hard to search for (probably a good thing in a deeper sense, honestly). So, what effects on hand/body would this have?

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  • $\begingroup$ Difficult to say, but search "hand electric shock injury" on google images with safesearch off, and well, it's not pleasant. $\endgroup$
    – Dragongeek
    Jul 24 at 14:30
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    $\begingroup$ 1 kilovolt at 1 kilofarad. What hand? I don't see no hand, I see an arm stump. One farad: one coulomb of electrons (one amp) for each 1 volt of pressure. 1,000 times 1,000 is a LOT of amps in a fraction of a second. Research: being hit by a full lightning bolt. Think: tree trunk hit by lightning. Think: higher temperature than the Sun. $\endgroup$ Jul 24 at 22:53
  • $\begingroup$ NOTE: Lithium Ion batteries are, in essence, capacitors. Think in terms of enough Lithium Ion batteries in series to produce 1,000 volts (electric cars are around 600 volts) and enough in parallel to produce 1,000 instantaneous amps (1,000 farads). Human SKIN is a great insulator, but pierce the skin (milometers) and you have essentially water, and excellent conductor. Think: scratches, blemishes, insect stings, zits, etc. $\endgroup$ Jul 24 at 23:13
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Normal mains-voltage (240/110 volts) is easily sufficient to cause a shock, that's unpleasant and potentially somewhat dangerous, but because of the resistance of skin which can be anywhere between 5KOhms to several million Ohms, the current flow is usually insufficient to cause any tissue damage.

The skin's insulating ability is the body's greatest protection against shock, the standard voltage thought to be sufficient to breakdown the skin's resistance would be 500v, now 1000 volts would likely cause fine puncture wounds in the surface (at first, they'd spread fast) which would then allow high currents to flow within the tissues itself causing tetanic contractions of the muscles (and as it's direct current, a grip you can't let go), heating, carbonization of channels through the flesh and the flow of very large currents, eventually eating away through the flesh creating a crazed fractal pattern:

enter image description here

https://cutthewood.com/ Fair usage 2021.

There would be out-gassing as the flesh burned, probable bloating, like the skin on a chicken that gets a gas bubble when you take it out of the oven. Then smoke as the flesh burns.

This would take no more than a few seconds. A Kilofarad capacitor charged to 1000v would discharge pretty fast - so the outgasing might be quite dramatic, and you would see the skin glowing orange as it carbonized. This video illustrates, though it's a low current source, the effect on flesh would be faster and more dramatic, and glow brighter (though I've not tried it myself, there'd likely be many small jets of flame-like plasma after the initial steam).

The flesh would lose integrity and tendons would detach, or finger joints allowing the hand to be pulled free. There would be lots of permanent damage to flesh, sensory nerves and muscles of the forearm.

Speculation:

It's possible, maybe just possible, that if the person who's hand touches the electrodes has engaged in lots of manual work and has very thick skin - like a builder or even gymnast, that the skin will be thick enough to prevent breakdown for a while, meaning, if the skin is dry there'd be a painful shock and tetany (and gripping if they were unlucky), but they might get away with little more than a pain memory.

If there were gripping, they might have several seconds or even minutes to cut the current/free the hand before the skin did break down (which it would do eventually).

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  • $\begingroup$ "A Kilofarad capacitor charged to 1000v" ok.. and I agree with the biology part.. but are you sure these capacitors actually exist ? electronics.stackexchange.com/questions/365768/… $\endgroup$
    – Goodies
    Jul 24 at 14:16
  • $\begingroup$ The specified tech level was one where it exists, but I up-voted your frame challengey answer. @Goodies A mega coulomb is enough to do the job as I described it, I'm pretty sure. $\endgroup$ Jul 24 at 14:44
  • $\begingroup$ Issue is, a high voltage is needed to hurt humans, because of our skin and body resistance, you accurately pointed that out. Higher capacity (in Farad) of the capacitor only increases the total amount of coulombs helt in the capacitor, it will not increase the discharge voltage. That voltage is determined by (equal to) the charge voltage. To allow for high charge voltages, dielectric surfaces should be thick. In a supercapacitor, this is not the case, unless you make it the size of a house. Can't tell these don't exist, but it would be quite exotic. Maybe such capacitors are used at CERN.. $\endgroup$
    – Goodies
    Jul 24 at 15:24
  • $\begingroup$ Pretty sure they'd be enormous, house may be an underestimate unless they live in mansions where you are. I'll look into it further, see if I can find the state of the art dielectric these days. @Goodies $\endgroup$ Jul 24 at 15:41
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    $\begingroup$ Even the NASA one (they're involved somehow in the development or funding thereof, with an appropriate breakdown voltage, you'd need a thickness of at least a mm, severely limiting the charge per area. No-one's bothering with high voltage applications, so there'd always be an inverter in the way of direct discharge like this, unless: rule of cool. @Goodies $\endgroup$ Jul 24 at 15:55
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Capacity matters less than max voltage does

As a former electronics hobbyist and electronic component collector, I can say from experience that much smaller capacitors can be quite dangerous, because they are suitable for high voltages. Even with normal consumer elco capacitors, like the the ones used in back in the 60's for TV power supplies. Capacity of these elco's ranged from 100 micro Farad to say, 0.01F for the really big ones, voltage max e.g. 400V. Triodes and Pentodes were involved, that's why they were made for this voltage range. These capacitors could become quite dangerous to handle, when loaded up with the TV's power supply.

Supercapacitors work with low voltages

In a supercapacitor, which could be 100-200 Farads, you could store lots of Coulombs charge. But generally, the max charge voltage of these components is very small, yielding much lower energy content. High voltages cannot be used, because that would pierce the dielectric surfaces in a supercapacitor. It would be huge size.. or special technology. The discharge voltage would be equal to the charge voltage and as a result, touching the electrodes does not have grave consequences.

I can refer to another answer. For supercapacitors, most common is 2.7 Volts.

https://electronics.stackexchange.com/questions/365768/why-arent-there-any-400v-ultracapacitors

Supercapacitors allowing for higher voltages are very rare and expensive. I found below one, it is 130F and it can handle 62.5V. A voltage like that would certainly be felt on the skin, but it will not kill you. And look at the price of this baby..

https://nl.rs-online.com/web/p/electric-double-layer-capacitors/1797440/

If higher voltages would be allowed, supercapacitors would replace batteries immediately ! They are much more durable than batteries, a capacitor can be charged millions of times, a battery cannot. For backgrounds,

https://www.tecategroup.com/products/ultracapacitors/ultracapacitor-FAQ.php

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  • $\begingroup$ A lithium ion battery is, in fact, a capacitor. Usually a cell is just over 3.7 volts. $\endgroup$ Jul 24 at 23:00
  • $\begingroup$ Not quite.. in batteries, the voltage remains a certain value, dependent on the construction and the chemical substances the battery is made of. If you would place 100 lithium ion batteries in series, the assembly would become dangerous to handle ! In capacitors, the voltage is dependent on the load voltage and variable below a certain limit.. this limit is the max voltage that can be applied before the dielectric surfaces are damaged, or start to leak excessively (internal resistance becomes low) $\endgroup$
    – Goodies
    Jul 27 at 8:13
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I could say a lot, but if an image is worth a thousand words, then a video is worth a million.

Here is a guy playing with four supercapacitors each rated at 2.6 kilofarads - so 2.6 times over your specs.

Soldering a coin with supercapacitors That was a nice coin

If you short one of those that is fullly charged, you get some sparks that look like what you get while soldering iron - nice stuff, could severely burn your hand and wrist maybe to 3rd degree, but nothing cinematographic. With four of those in tandem, though... watch as the guy connects those to random stuff, including a circuit board and a dime. Now that's where the fun really begins!

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    $\begingroup$ That spark is dangerous indeed, but I'm afraid it is no answer. This can burn your hand, but what you see is the result of shortcutting the capacitor. An enormous current flows through low resistance metal, at low voltage. Energy will be released as heat. Actual voltage remains below 10V. You can make metal wire glow with a consumer 9V battery. If you would put your finger on the metal, it would burn too. But when the electrodes only touch your thumb and ring finger, no metal involved, the current will be near zero, because the resistance of your skin is far higher than that piece of metal. $\endgroup$
    – Goodies
    Jul 24 at 14:02
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    $\begingroup$ The catch is that 1Kv is a lot more than 9v, and the current through your finger would be about 100x with the supercapacitor OP describes. Skin contact resistance is about 500 Ohms so that's 1 KOhm in total. At 1Kv that's only 1A of current but that's 1A at 1000V which gives us 1000W which is a whole lot of energy. $\endgroup$ Jul 25 at 3:08
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    $\begingroup$ @Goodies But he's got 1000V behind it. That's enough to cause skin breakdown and you're looking at a few hundred ohms--several amps, that's thousands of watts. Now you've got even less resistance and even more power. How fast can the capacitor dump it's power? $\endgroup$ Jul 25 at 3:14
  • $\begingroup$ You'd would never be able to discharge at a level of 1000 volts. For a capacitor, the discharge voltage is (max !) equal to the loading voltage ! And a loading voltage of 1000V is not feasible with a supercapacitor. See above, the device would become enormous. The energy the capacitor would be able to hold is limited. $\endgroup$
    – Goodies
    Jul 27 at 8:02

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