[TriLUG] On Electrocution (was: Re: recommendations for UPS 12V batteries?)

[Brian via TriLUG]

On 4/18/20 1:55 PM, Pete Soper via TriLUG wrote:
> Current can be just as dangerous as 
> voltage. 

It's current that kills you.  Voltage is only the "potential" to create 
current; nothing happens until the electrons start moving.  A 12-V car 
battery can easily melt a large wrench but won't hurt you if you touch 
the terminals*.  A nine-volt battery with subdermal contact can be fatal.

i.e. be very careful with your high-range ohmmeter if it has 
insulation-piercing probes!

And since we're on the subject:

First, always be careful with any power source.  But with that said:

DC is relatively safe up to some hundred volts in brief contact with 
unbroken dry skin.  Dry skin has a relatively high resistance (on the 
order of 100 kOhms).  Note that for many of us sweaty-palmed types, our 
skin is actually rarely really "dry."  Also, resistance is inversely 
proportional to contact area, so a larger contact patch means lower 
resistance.  So, be careful.

Low-frequency high-voltage AC (e.g 60 Hz "house current") is extremely 
dangerous, as it will capacitively couple right through your body and 
kill you dead.  So, be careful.

High-frequency high-voltage AC (several thousand Hz, e.g. a tesla coil) 
is much less dangerous; although it can still capacitively couple 
through your skin, the "skin effect" will keep current flow around the 
perimeter of your body, mostly away from your heart.  It'll still burn 
and damage you badly, but most likely in a nonfatal way.  So, be careful.

See https://en.wikipedia.org/wiki/Electrical_injury for more gory details.

And be careful!

:-)

-B

* - with dry hands