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I have stumbled upon interesting discussion in the commentary section regarding safety of electrical engineering in home environment.

person1: AC voltage 'flows' even through insulator, fact.

person2: Yes? How is it possible the current won't electrocute you after you plug in the mixer into socket wall?

person1: Because of a low capacity between me and the conductor, however the capacity between the ground and human standing on the insulator is vastly higher. If you are interested, have a look at the capacitance / functioning of the capacitor.

Can you tell me who is right and why - please elaborate with scientific arguments.

I guess the first person is right. Similar situations would be a person standing under high voltage transmission lines, yes there would be increased electromagnetic radiation while standing, but still it would not electrocute, unless you touch the cable above (transmission line) while standing even on insulator laid on the ground. This way it would create large potential gap and the result would be you either transforming into carbon or having your heart arrested.

Am I right? Can you explain how potential diff (voltage) relates to capacity? Do these affect each other mutually (linearly, exponential dependence)?

I have masters in telecommunications, but this question really intrigued me.

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    \$\begingroup\$ Please estimate the capacitance of said mixer + chord to ground/air and calculate how much current would flow there at 50 or 60 Hz at any mains voltage. Compare that with how much current is needed though a human to hurt him/her. \$\endgroup\$
    – winny
    Commented Jul 4 at 12:40
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    \$\begingroup\$ the second person does not make a starement ... only the first person can be wrong or right \$\endgroup\$
    – jsotola
    Commented Jul 4 at 12:40
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    \$\begingroup\$ Voltage doesn't "flow", so neither is making truthful statements. \$\endgroup\$
    – Finbarr
    Commented Jul 4 at 12:49
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    \$\begingroup\$ "Electrocution is death or severe injury caused by electric shock from electric current passing through the body" ... not everything will cross the threshold for "electrocution", but you may still get energy coupled into your body, ranging from no sensation / awareness at all, to tingling, all the way through to "death or severe injury" and beyond. \$\endgroup\$
    – Attie
    Commented Jul 4 at 12:54
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    \$\begingroup\$ Note that the term is "capacitance"; "capacity" is not used in this form in English. \$\endgroup\$
    – Hearth
    Commented Jul 4 at 23:45

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person1: AC voltage 'flows' even through insulator, fact.

False, category error. Voltage doesn't flow, current flows. We could say that it's sort of true about insulators, if you are allowed to confuse the terms like voltage and current, as AC current can flow through an insulator. However, if you are confused between voltage and current, then anything else said about electricity should be ignored.

person2: Yes? How is it possible the current won't electrocute you after you plug in the mixer into socket wall?

person1: Because of a low capacity between me and the conductor,

True. The low capacity allows only a very small current to flow, too small to damage you, at least in the case of a 2-pin, non-earthed, mixer. If it's a 3-pin earthed mixer with a metal case, the case will intercept the capacitance from any live conductors to a user, routing the current to ground instead of you.

however the capacity between the ground and human standing on the insulator is vastly higher.

True, but irrelevant to the question. It reduces the AC potential the person has with respect to ground. Higher capacity to ground however actually means higher AC current flowing through the person from the capacitance to the mixer, so it has the opposite effect to what the speaker seems to be asserting.

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  • \$\begingroup\$ I've follow up questions...I understand everything in other answers and adjunct comments, but for your answer: Why's there a low capacitance between human and the mixer's conductor? Capacitance depends on surface area and reversely on distance. Even if I hold conductor with bare hand while using mixer, is there a low surface area? Regarding last blockquote, can't get it at all. I always visualize dielectric/insulator between 2 wires=capacitance model example. What are the wires and what is the dielectric in that case? Explanation's missing on higher capacitance on the last blockquote. \$\endgroup\$
    – Tony_12652985
    Commented Jul 10 at 20:47
  • \$\begingroup\$ @Tony_12652985 I'm sorry you don't get it. With hand-wavy diagrams adn questions, it can be difficult for different people to make the same assumptions and come to the same conclusions. The last block quote in my answer is directed at the lower capacitor in the capacitive divider from source, to human, to ground. Increase thst, and the potential of the human decreases, although the total current through the divider increases.. \$\endgroup\$
    – Neil_UK
    Commented Jul 11 at 6:05

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