I am aware that current is very dangerous and only 0.2 amps is enough to stop a heart. However I always see that high voltage is dangerous. Tasers produce a high voltage but since there is low current it is considered safe. How is it possible? According to Ohm's law, Current is equal to voltage divided by resistance (I=E/R). So if you are being tased by 10,000 volts and your resistance is only 1000 ohms, wouldn't there be 10 amps flowing through you and killing you? (10,000/1000= 10)
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The voltage drops as soon as you touch it. – user253751 Mar 05 '18 at 03:53
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There's more than just the Ohm's law to the interaction between current and human nervous system. Here's [one of my favorite posts on that subject](https://electronics.stackexchange.com/a/158610/7036). – Nick Alexeev Mar 05 '18 at 03:59
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@immibis. Not if there is enough current. I smell skin burning... – Mar 05 '18 at 03:59
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@Sparky256 *For a safe high voltage,* the voltage drops as soon as you touch it. Otherwise it is not safe. – user253751 Mar 05 '18 at 04:04
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10ma can stop a heart, if that heart is up a ladder or falls in water. – Harper - Reinstate Monica Mar 05 '18 at 04:05
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@Sparky256 Whether the skin will burn or not depends on current *density*. This is put to use in electrosurgery. I can run a 2A current (100V, 500kHz) through a large enough electrode without causing too much heating at that electrode. The other electrode can act like an scalpel that cuts and cauterizes [i.e. burn] the tissue. – Nick Alexeev Mar 05 '18 at 04:07
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Then it is in Gods hands. I know a man who grabbed the phase A and C bus bars of a 600 vac SPD unit, and lived. But the bus bar shape is burned deep into his hands. – Mar 05 '18 at 04:07
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@NickAlexeev. I agree. If you are 6 feet tall you have 200 volts from head to toes when under a thunderstorm cloud, but we are used to it, and it is spread over the body. – Mar 05 '18 at 04:10
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The key seems to be current limiting and distribution of current, assuming it is 10KV or more. – Mar 05 '18 at 04:13
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Safety standards are different for a taser from an ordinary electrical appliance.
The whole point of a taser is to have an adverse effect on the human body, and a small fraction of people who get tased do die from it. This risk is considered acceptable (by some people), since the alternative is for the taser user to use a gun or nightstick instead, either of which has risk of death.
However, if you are designing a kitchen appliance or a television set, if it has the same effect on its user as a taser, that would be a gross failure, and an unacceptable risk.
The Photon
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A Taser over the heart or the back of the neck is considered possibly fatal. It may stop the heart. – Mar 05 '18 at 04:02
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Ahh so that's how to abuse a taser eh LOL @Sparky256 - the cat is out of the bag so to speak! – Andy aka Mar 05 '18 at 11:42
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Let's look at other things which work this same way. A metal-halide light is a type of arc-discharge light. Like most arc-discharge lights, it is practically a dead short once the arc is struck. So why doesn't a metal-halide light basically explode once it ignites?
Because it is fed from a current-limiting power supply.
Most HID lights use a magnetic wound-transformer ballast, which is rigged to limit current. But HID ballasts do exist which are electronic, and do the same thing with semiconductors. These are similar to LED driver modules, except with additional features to strike the arc and warm up the bulb.
Similarly, taser control modules hit the victim with enough voltage to strike the arc, then limit current to "correct" values.
Harper - Reinstate Monica
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@Sparky256 "taser control modules hit the victim with enough voltage to strike the arc, then limit current to "correct" values. " – user253751 Mar 05 '18 at 04:23
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wouldn't there be 10 amps ?
Maybe for the 1st few nanoseconds, but
No
Your question is too vague to answer all conditions to make it safe.
Make what safe? A taker?
Most of the Electro muscular currents bypass the heart from external dielectric mass. So they might use 10k more energy to start a heart in Emergency than in open heart surgery.
The source impedance limits the current to desired levels, while high initial voltage ionized the contact to lower contact impedance.
Safety of insulation depends on medium (3kV/mm for clean air) and electrode or bushing geometry which has 5:1 effect from smooth donut to sharp needle for E field gradient stress.
Distribution capable of 10kA *600V is capable of human arc flash is many orders of magnitude more unsafe than 100kV @ 10mA.
But a transformer substation with 200kV basic impulse limit (BIL200) protection will protect yet fail with 60kV at line f on a 40kV grid due to insulation strength raised by source rise time from ionization delays.
All line powered products Must be factory tested to safety Hipot leakage tests in each country in the range of 3kV with <100uA expected except for line filters up to 250 uA per power supply.
Tony Stewart EE75
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V does equal IR...
Have you ever picked up a 1.5V AA battery like this?
If the resistance between the terminals, was say 10 Ohms then we would potentially have 0.15 amps flowing... getting close to that "heart stopping 0.2amps" right?
Well, the thing is that the current is always going to take the shortest (lowest impedance) path, which in this case would be from the second finger to the thumb, which is a long way from the heart.
According to this article https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2763825/ The resistance of dry skin is about 100,000 ohms and "internal body resistance" is about 300Ohms..
So putting these two facts together: 1) resistance of skin is quite high 2) current will take the shortest (or lowest impedance) path between two points
we can see that being short by a taser is not likely to stop the heart (unless the probes end up either side of it).
AugustCrawl
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Many things don't act like resistors when high voltages are involved. – user253751 Mar 05 '18 at 04:16
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The lowest impedance path between the two taser prongs is unlikely to be through the heart. I thought the picture helped show that? – AugustCrawl Mar 05 '18 at 04:27
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Current always explores **ALL* possible paths, not just the shortest or the lowest impedance. – analogsystemsrf Mar 05 '18 at 04:47
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@analogsystemsrf but when people have been hit by lightning, the current can be seen to have chosen the path of least resistance - as evidenced by the burn marks, but if your assumption is true then they should have an even burn pattern over all the skin surface... "Current always explores *ALL possible paths" – Solar Mike Mar 05 '18 at 04:52
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@SolarMike The current through a path is inversely proportional to the resistance of the path. – user253751 Mar 05 '18 at 05:03
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Another relevant factor is that we think of current in Coloumbs per second, however the taser pulse is very short (microseconds).. see page 32 of this for details http://www.ecdlaw.info/outlines/11-10-08%20Brave%20ECD%20Appendix%20FIN.pdf – AugustCrawl Mar 05 '18 at 05:39