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Comment by james400 | Hacker News Reader

"It's not the voltage that kills you, it's the amps!" Wouldn't power (W) (or joules) be a better way to phrase it? Because as you said, you can't have 100mA flowing through your heart unless you ALSO have stiff enough source to actually supply that current - which implies a high compliance voltage, can't escape ohms law.

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No, it's not the power, either, as low resistant paths can be extremely dangerous (such as wet skin). Really, it's a 2 dimensional space that makes for a less catchy aphorism. "It's not the voltage that kills you, it's the combination of voltage and conductivity".

Honestly I kinda hate that saying. It's like "it's not the fall that kills you, it's the sudden decelleration on impact." For most situations people encounter, it's high voltage sources with more than enough power which are dangerous.

"The combination of voltage and conductivity" is ... current, no?

GP mentioned impedance, not resistance. You won't feel anything touching the 12/24V terminals in your car because they're DC. Your skin has a high resistance, but when faced with AC, has a low impedance. This makes AC much more dangerous, as you conduct 120V AC much better than 120V DC.

Even 50mA will likely kill you, as outlined on the "death graph" as we electricians call it. This is independent of voltage.

https://upload.wikimedia.org/wikipedia/commons/7/7f/IEC_TS_6...

Blue is harmless and imperceptible, green is harmless, yellow is harmful, red is fibrillation.

Edit: This illustrates why 30mA (or less) RCD protection is common (and required) in various jurisdictions, depending on the kind of circuits you're serving.

Right, and in particular, "Type B" RCD protection is required for solar inverters in various jurisdictions. These provide protection against DC fault currents.

> This makes AC much more dangerous, as you conduct 120V AC much better than 120V DC.

But at higher frequencies, you should experience the skin effect, right?

I can't answer that question, as I'm only an electrician, not an electrical or RF engineer.

That said, we're referring to power delivery here, and the highest frequency I'm aware of in this space is the 400 Hz power distribution systems used on warships.

Not really, whether it takes 50V with wet skin or 500V with dry skin, it's the current that kills you, not the watts

Here is medhi sadaghdar (electro boom) putting 11v at 150A through his tongue https://www.youtube.com/watch?v=XDf2nhfxVzg

The voltage across the heart will be rather bounded if you fix the current at 100mA, though. Hearts will not differ significantly from each other.

"It's the volts that jolt, but the mills (mA) that kills" - The phrase a schoolteacher used when I was a lad.

V = I * R

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