Question about Amperage

[amptramp]

There is a case of a guy who used probes that pierced his skin on each hand, connected himself across a standard 9-volt battery and electrocuted himself.

Commercial aviation (and even the Space Shuttle) used 28-volt power for almost a century now.  This is two 12-volt lead-acid cells in series being charged from the on-board generator so that each battery is at 14 volts.  The military considered 30 volts DC to be the threshold of danger (but MIL-STD-705 allowed for voltage surges of up to 32 volts when loads are switched off).

AC tends to cause heart fibrillation whereas DC tends to stop the capability of breathing.  You really don't want either situation.

[karbomusic]

There is a case of a guy who used probes that pierced his skin on each hand, connected himself across a standard 9-volt battery and electrocuted himself.

Though that sounds far fetched (would love to see the actual details), I believe you. However, there is something very Darwinish about that statement.

Of course I'd probably get yelled at by everyone for being an avid 9V battery "licker" but since I've been doing it for 45 years (literally) it sort of is what it is.

[PRR]

> *Dry* skin is resistive.

Over 100K to below 10K.

> Its resistance drops dramatically when it's wet or broken.

*OR* if a "small" current continues to pass. Very low "safe" currents can break-down cell walls a little. Then the salt-water leaks out. The "dry" skin is now very wet and conductive. Total resistance drops from maybe 100K down to less than 1K. If the source is constant-voltage (most are), then the current rises very high after the cell walls go weepy.

You see this if you read enough electrocution reports. Bystanders or the position of the body suggest the victim had felt a "tingle" for some little time before the death. Insufficient data and too much variability to even guess how much tingle for how long will be fatal.

That's why 24V-30V shocks are sometimes fatal, when calm dry skin resistance of >10K says they can't pass even 5mA. The 10K falls to under 1K and that's well into the danger zone.

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42V in a drain-down test may imply it will continue to drain down, be below 24V or 9V reasonably soon. In today's safety climate, 42V steady probably should not be on exposed terminals.

I can "feel" a 12V car battery on a really sweaty day.

The more popular problem with car batts is, as you say, if you get your ring across the leads it will burn your finger to the bone. And as Jimmy Fallon just found out, with any real-serious all-round finger injury, "Usually they just cut your finger off."

[Jdansti]

^ Rings can lead to bad injuries through electrocution, becoming super hot when they short a circuit, when they get snagged during a fall or by a piece of machinery, or when they get crushed.

I know a guy who was on a tall ladder working on a light fixture who fell and his ring got caught on the fixture somehow. As he fell the skin and some flesh on his finger was peeled off and turned inside out.

My wife's ring was crushed when she and a coworker were walking to a restaurant for lunch and she tripped and fell. Her friend stepped on her hand and crushed the ring onto her finger. Her finger swole up and she had to have the ring cut off at an emergency room.

Bottom line-don't wear jewelry when working around electricity, machinery, or with tools. Not much you can do about falling and someone stepping on your hand, though.

[R.G.]

Not much you can do about falling and someone stepping on your hand, though.

Actually, there is. You can have a jeweler cut a "break-away" slot on the inside of your rings so that any significant force or deformation will break the ring there. Kind of a "mechanical fuse". It requires making a conscious decision about whether the ring or a finger is more valuable though. 

I'm not sure what to do about those rings I've seen made out of tungsten carbide.   

[Jdansti]

^Good idea. Maybe my wife will let me cut a breakaway in her ring with my Dremel tool.