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I just read on a website that 5mA is enough to give a little shock but I have touched 650mA and nothing happened. Does that mean that 650mA becomes too small when I touch it due to resistance of my body? So, how many amps would give a shock?

Mohammad Taha
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    You can't "touch" 650mA. How do you even think you're doing that? – Finbarr Aug 15 '17 at 09:29
  • 650 mA was the result of the resistance of your body to the applied voltage. Moreover, if you had a exposition to 650 mA across your body, you are not writing here. – pasaba por aqui Aug 15 '17 at 09:29
  • What do you mean by "I have touched 650mA"? If 650mA entered you left hand end exited at your right hand you'd be probably be dead. – Curd Aug 15 '17 at 09:30
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    Possible duplicate of [Is 20 watts of electricity dangerous?](https://electronics.stackexchange.com/questions/158603/is-20-watts-of-electricity-dangerous) – user Aug 15 '17 at 09:32
  • You have touched a power supply with some voltage and a current rating of 650 mA. Luckily the resistance of your body was high enough and the voltage low enough. So not all the current was flowing. If you'd touch an ideal current source of 650 mA, you'd probably be dead. – Arsenal Aug 15 '17 at 09:32
  • @MichaelKjörling *650 mA is not high current* Now let that 650 mA current flow between your left and right arms (straight through your chest and heart) and then write that again. Very likely you cannot do so as you'd be **dead**. To make 650 mA flow between your arms I might need 10 kV but no one said anything about the voltage. – Bimpelrekkie Aug 15 '17 at 09:37
  • @Bimpelrekkie So you're saying that it is correct to tag a question asking about 650 mA (at some unspecified, but presumably nowhere near kilovolts or more) "high current"? Not arguing, just like to understand the boundaries of the tag. – user Aug 15 '17 at 09:39
  • @pasabaporaqui I'm not saying it *isn't dangerous*. I'm wondering if tagging this *high current* is appropriate. – user Aug 15 '17 at 09:40
  • Reference "Factors in lethality of electric shock", https://en.wikipedia.org/wiki/Electric_shock#Factors_in_lethality_of_electric_shock – pasaba por aqui Aug 15 '17 at 09:45
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    @MichaelKjörling "High current" or "Low current" is relative. As an IC designer, 100 mA for me is a high current. For someone working on electrical locomotives 100 mA is **nothing**, for them 1 kA is "normal" and 10 kA could be a high current. So without describing the context I'd prefer not to make the high/low distinction and/or use a tag. – Bimpelrekkie Aug 15 '17 at 09:46
  • @Bimpelrekkie: we can average 2Kohm the resistivity hand to hand across heart. Thus, 220v / 2k = 110 mA (a few dead), 1000 v / 2k => 500 mA (very dead), 12000v/2k = 6A (serial killer) – pasaba por aqui Aug 15 '17 at 10:01
  • @pasabaporaqui The trick is to get such a low resistance. The human skin is the problem, you'd need some very nasty way (horrific I'd say) of connecting your DUT (the human) to get down to 2 k ohms. – Bimpelrekkie Aug 15 '17 at 10:10
  • @Bimpelrekkie: see https://en.wikipedia.org/wiki/Electric_shock#Body_resistance for measures of body/skin resistance. – pasaba por aqui Aug 15 '17 at 10:13

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I have touched 650mA

No, you haven't.

You may have touched something that was capable of delivering 650 mA if the load demanded it. Your body will draw current proportional to the voltage applied to it and inversely proportional to its resistance. The current capability of a supply is irrelevant, assuming it's more than what your body it trying to draw.

For example, it's generally safe with dry hands to touch the terminals of a 12 V car battery. That battery is capable of several 100 amps to crank the starter, but your body will draw well under a milliamp.

It's the current thru you that you feel and that can hurt you. High voltage is dangerous because it forces more current thru you. Likewise, wet skin is equally dangerous because that greatly decreases the body resistance, allowing more current to flow at the same voltage. You can kill yourself with one of those little 9 V clip-on batteries if you do the right (wrong) things.

Olin Lathrop
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  • To be exact, is the current, the duration and the path across the body what can hurt you. As additional example: a door knob or a plastic can have a static voltage of more than 20000 v, but causes no dead due to its brief duration. – pasaba por aqui Aug 15 '17 at 10:06