I've read that if someone is electrocuted by the prongs of a plug, that's not usually lethal, but it becomes a lot more dangerous if someone is grounded by touching metal (and also being wet? but that seems like something different entirely).

Does this mean that touching any metal object makes the electrocution significantly more dangerous? For example, if someone was touching car keys sitting on a table and they were electrocuted at the same time, would the car keys make the situation a lot more dangerous? Or is it only more dangerous when touching things that are plugged in, faucets connected to a plumbing system, etc.? Why does the grounding make things more dangerous, and how much more dangerous is this?

  • \$\begingroup\$ The danger comes when the current flows near to your heart because that can cause it to stop beating. Current always takes the easiest route so make sure that it takes a less lethal route through you! \$\endgroup\$
    – Finbarr
    Apr 6 '17 at 9:26
  • \$\begingroup\$ VTC - This question does not fall within the range of Electronics Design topics entertained at this site. A modicum of web searches with the likes of Google will turn up plenty of information regarding high voltages and electrocution hazards. \$\endgroup\$ Apr 6 '17 at 9:26
  • \$\begingroup\$ @MichaelKaras I actually voted the same; but safety considerations are so very close to design, that I think this question is on-topic. In the end, we wouldn't close a question that asks "I need to improve the safety of my circuit, so, I'd like to first understand the risks involved in electrocution; {description if device}". OP didn't do that, mind you, but this question is actually useful for people with the question I asked that (hopefully) search the site. \$\endgroup\$ Apr 6 '17 at 9:34
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    \$\begingroup\$ Possible duplicate of How grounding works to prevent electrical shock \$\endgroup\$ Apr 6 '17 at 19:12

electrocution isn't the act of you touching something, but the act of current flowing through your body.

Current flows from somewhere to somewhere.

So, in the examples you bring, current flows from the plug, through your body, to the ground.

If there's no ground connection, nothing happens (ok, you might feel it shortly when your body gets charged, much like a spark from a rubbing-charged balloon). That's why birds can sit on high-voltage lines without being roasted instantly.

If you're "somewhat grounded", you have a high resistance in the plug->body->ground circuit. (I say circuit, because at the "other end" of the plug, there's a power plant, which also has a (virtual) connection to ground, so the loop's closed.)

High resistance means at the same voltage, less current flows. If you've now got wet hands, the plug->skin->body resistance gets very low. If you're standing in rubber boots, the body->ground resistance gets high, but if you stand on a steel tower with sweaty feet –> baaad news.

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    \$\begingroup\$ I'd add. dry skin is actually quite a good insulator. Simple test, touch you skin with the terminals of a standard 9V battery. You feel nothing... now try that on your tongue. \$\endgroup\$
    – Trevor_G
    Apr 6 '17 at 14:45
  • \$\begingroup\$ so what things are grounded? surely it's not literally anything that's metal...but I hear metal commonly cited as something makes you grounded. are doorknobs grounded? are metal chairs grounded? \$\endgroup\$
    – user144522
    Apr 6 '17 at 16:33
  • \$\begingroup\$ this might sound stupid, but: anything with a conducting connection to ground (or every conductor that is sufficiently big to count as ground) \$\endgroup\$ Apr 6 '17 at 16:48
  • \$\begingroup\$ @Trevor That is only true for very low voltages. \$\endgroup\$ Apr 6 '17 at 18:54
  • \$\begingroup\$ @DmitryGrigoryev, obviously if V is high enough the skin layer is not going to help. But still, wet skin is far more conductive than dry. \$\endgroup\$
    – Trevor_G
    Apr 6 '17 at 18:57