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Got shocked by 120VAC
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VK3DRB:

--- Quote from: Siwastaja on June 05, 2021, 12:58:19 pm ---
--- Quote from: Quarlo Klobrigney on June 04, 2021, 12:34:22 pm ---120V is irrelevant. It's the current that kills. The voltage just breaks the skin resistance to help kill you.

--- End quote ---

I wouldn't expect to read this bullshit on the EEVBlog forum...

Voltage is what defines the current that flows through the (complex and nonlinear) impedance of the human being. That's exactly why all the safety regulations are based on voltage. Safety voltage / extra low voltage limit for 50/60Hz AC being roughly around 40-60V depending on the jurisdiction. See https://en.wikipedia.org/wiki/Extra-low_voltage

Anyway, comment about delayed arrhythmia is a good one. It's always a good idea to get checked if in doubt.

--- End quote ---

He is correct in that it is the current that kills. But it is related to voltage of course, so 120V is not irrelevant.

Your comment reminded me of an argument I had with another engineer at the workplace lunchroom who thought he knew it all. OK, he had a PhD in electronics engineering and I only had the degree. But I knew what I was talking about. IBM Australia years earlier placed every engineer on an electrical safety course. I learnt then that 20mA through the body can easily kill a person by electrocution. The PhD refused to believe me that so low current can kill a person, saying it would take several hundred milliamps. You could not argue with this guy who was a little arrogant, but I refused to backdown. Unbeknown to me, he decided to research it for himself.

Two days later, in front of my peers at the lunchroom table, he apologised publicly, admitting he was wrong and I was right. It was a complete shock (no pun intended). From that day on, he was never argued or was arrogant with me again, and we ended up becoming good friends.

GlennSprigg:

--- Quote from: VK3DRB on June 13, 2021, 12:16:00 pm ---
--- Quote from: Siwastaja on June 05, 2021, 12:58:19 pm ---
--- Quote from: Quarlo Klobrigney on June 04, 2021, 12:34:22 pm ---120V is irrelevant. It's the current that kills. The voltage just breaks the skin resistance to help kill you.

--- End quote ---

I wouldn't expect to read this bullshit on the EEVBlog forum...

Voltage is what defines the current that flows through the (complex and nonlinear) impedance of the human being. That's exactly why all the safety regulations are based on voltage. Safety voltage / extra low voltage limit for 50/60Hz AC being roughly around 40-60V depending on the jurisdiction. See https://en.wikipedia.org/wiki/Extra-low_voltage

Anyway, comment about delayed arrhythmia is a good one. It's always a good idea to get checked if in doubt.

--- End quote ---

He is correct in that it is the current that kills. But it is related to voltage of course, so 120V is not irrelevant.

Your comment reminded me of an argument I had with another engineer at the workplace lunchroom who thought he knew it all. OK, he had a PhD in electronics engineering and I only had the degree. But I knew what I was talking about. IBM Australia years earlier placed every engineer on an electrical safety course. I learnt then that 20mA through the body can easily kill a person by electrocution. The PhD refused to believe me that so low current can kill a person, saying it would take several hundred milliamps. You could not argue with this guy who was a little arrogant, but I refused to backdown. Unbeknown to me, he decided to research it for himself.

Two days later, in front of my peers at the lunchroom table, he apologised publicly, admitting he was wrong and I was right. It was a complete shock (no pun intended). From that day on, he was never argued or was arrogant with me again, and we ended up becoming good friends.

--- End quote ---

Thank you. It's not rocket science, or bragging about 'knowledge/power', or deliberate 'put-downs' when us 'mere-mortals' dare to say something...
Responses like...  "I'm not interested in social games. I prefer intellectual honesty so work it out in your own head."...  and "Think about all of this instead of playing social games.",
and ... "...instead of making up our own straw men to then knock over."... W.T.F. ??  I wish these 'Tower-Climbers' would climb down the mountain a bit...
Quarlo Klobrigney:
The irrelevancy was to the fact of the 240V vs. 120V argument.
My comment was taken out of context. I was also relating to low voltage death.
I can put an idea forward and see who wold expand upon it.

I got an a nasty shock, similar to 120V when working on my van battery in a tight place, and being a hot summer day, I was sweaty perspiring excessively and got in between the battery cable and the post, and who knows in that tight spot, the chassis. Whatever current being drawn was it was enough to knock me on my ass.

Yes I am a native speaker having been born in the US and made it through the 12th grade and much more education than that.

So to sum up, I say the higher the voltage is, the easier it is to break through the skin's resistance which lets more current through to do the dirty work.
As another topic, RF burns being quite nasty as well having had a few myself.

In the very early 80's having had ~ +/- 2KV across the chest from a defective HV measurement probe (open ground) in the right hand, then out the left knuckle to the cabinet, it propelled me off the stool vertically. Weighing in at 150 pounds, gravity took over and I landed on my back some 6' away. Another person saw me "fly" through the air. It took a minute or so before all the white light, and the underwater sounds, for my senses and locomotion to return to normal.
All said person did was to watch and comment later after I got to my feet.

My experiences and the way I have lived them and what I have learned to be true in my life.

 \$\Omega\$ -30-

Quote from: VK3DRB on Today at 21:16:00
He is correct in that it is the current that kills. But it is related to voltage of course, so 120V is not irrelevant.



--- End quote ---
Siwastaja:

--- Quote from: VK3DRB on June 13, 2021, 12:16:00 pm ---Your comment reminded me of an argument I had with another engineer at the workplace lunchroom who thought he knew it all. OK, he had a PhD in electronics engineering and I only had the degree. But I knew what I was talking about. IBM Australia years earlier placed every engineer on an electrical safety course. I learnt then that 20mA through the body can easily kill a person by electrocution. The PhD refused to believe me that so low current can kill a person, saying it would take several hundred milliamps. You could not argue with this guy who was a little arrogant, but I refused to backdown. Unbeknown to me, he decided to research it for himself.

--- End quote ---

Nice story. This involves statistics and exact semantics; but of course, when it's about such serious matter as dying, you can't accept even 1% likelihood.

20mA won't that easily kill someone unless they have existing heart condition, or are just very unlucky. But if the question is whether it can kill someone, yes, you are then absolutely right. At several hundred mA, it just becomes very likely. So all he did wrong might have a slightly distorted mental image of the probability distribution, it doesn't need to be very far off.

There is a reason why 30mA is a popular choice for RCDs, it gives very good (albeit not perfect, but nothing is) defence against death by electrocution and won't nuisance trip too easily, but you are right, some oddball resistive path limiting current (and voltage!) could result in a continuous 20mA fault current through body for prolonged time which could kill an unlucky individual. A 10mA RCD would protect against such case, but then again, we might find an even more unlucky individual at the tail of the distribution function who can't take even 10mA.

Personally, I have received 230VAC (full-bridge rectified) hand-to-hand which would have had very high chances of being fatal, but a 30mA RCD really saved the day, and I can testify it's really efficient, the shock was surprisingly benign due to very limited time; for example, muscle pain in my arms that day was only slightly uncomfortable. No changes in heartbeat or nausea or anything like that. Glad it was a type A RCD, this wasn't obvious back then, type AC was still widely used and it wouldn't necessarily have tripped due to fault current going through a rectifier. Nevertheless, it was an extremely stupid thing to do, I had a mental image of a MOSFET bridge being isolated but the gate driver wasn't isolated, so there was a direct path from rectified mains, through lower leg MOSFET source, to the touchable control circuit side. Be very careful to completely understand the circuit, which is also why I stress the importance of understanding instead of learning rules and analogies by heart.
Siwastaja:
Finally, to set the record straight, the problem with the simplistic claim "it's the current that kills" isn't just that it's not correct, it's that it provides "wrong" level of abstraction which isn't very useful, and which is highly confusing. To make matters worse, it's very widely taught as some kind of "truth" which it just isn't.

Because if we take the viewpoint of the human body, then it's not right, you could say it's only half the truth but it's lacking so much I continue to call it "wrong". Using Van der Graaf generator or a cat, it's easy to demonstrate currents exceeding hundreds of mA go through body with absolutely no harm done. ESD currents are regularly in amperes, no biggie. So current clearly isn't what kills. Time, or the integral of the current, is equally important, these two variables are the bare minimum for a model describing what happens to the body, but the model gets better the more we add to it.

We can also take the more practical circuit design viewpoint of what circuits are safe, what circuits are not, and how to protect them, based on what criteria. This viewpoint is what legislation uses, and yes, because most circuits use low-impedance voltage sources, the mains supply networks, generators, batteries, solar panels being obvious examples, then the only sane thing is to base the safety rules on voltage, for example, consider <50VAC or <100VDC safe to touch, otherwise add reliable layers of insulation and/or earthing.

I'm truly surprised I'm discussing this on the EEVblog forum, though, and not in the beginner's section. I thought all of this is obvious for many here. I remember Dave calling "voltage kills" claim bullshit in some of his videos but may remember wrong.

I'm also surprised people take calling "bullshit" "bullshit" so personally given that this B word is so prevalent on this forum and on Dave's videos, but I may have missed some social factor I'm not too good in, maybe it's OK to call bullshit when it's about an outsider's video, or a post by some of the lower-class members, but I'm not aware of Quarlo's social status because I have no idea who he is and what he contributes here, so clearly I hit the wrong button here. This is why I said I don't like these social games.
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