[PSUBS-MAILIST] Thoughts on Volts and H2O was Compensation

["Gary R. Boucher" <protek@shreve.net>]

     I have on many occasions installed or modified some kind of 120 volt 
outlet by standing on an insulated surface wearing tennis shoes for extra 
protection (insulation) where I simply touched the live 120 volt wire with 
my bare hands and felt no shock.  But the reason was that the current had 
no path to ground.  This is dangerous and absolutely nobody should do this 
including me.  If I had touched the wrong thing with any part of my body 
like a sweaty arm I could have turned into an statistic.
     There is the time-honored argument of current versus voltage.  What 
kills you?  Actually, you can not separate current from voltage.  If you 
take a resistance reading from one hand to another with a volt-ohm meter 
you will find that it varies greatly based on the person, time of day, 
activity, humidity, etc., etc.  But given a certain reading in ohms, if you 
divide this reading into the applied voltage from a source you will get the 
current in amps.  If the voltage doubles, the current doubles.  If the 
voltage triples the current triples.  So is it voltage that kills or 
current?  The answer is simple; one can not exist without the other.  They 
are proportional to each other given any fixed resistance.  You could say, 
and be totally accurate, that low resistance kills.  Take that 120 volts 
that gives a small tingle if you touch it.  Had a person grabbed a bare 
metal rod with a salty-sweaty hand with bare feet on a grounded steel plate 
(also sweaty, yuck!) the person could easily be killed.  What 
happened?  His resistance killed him!!  It was lowered to a value that the 
same voltage allowed greater current.  You may say well it "Was" the 
current.  But, you would not had half that current with half the voltage.
     Although small currents can cause problems with heart rhythm and 
possibly death many people die because of physiological damage caused by 
the power they absorb.  Power is the product of voltage times current in 
watts.  Since the current goes up with voltage in proportion, you have two 
variables increasing that are multiplied together.  Thus power (the real 
killer in many cases) is proportional to the voltage squared or the current 
squared!  Actually (V^2)/R or (I^2)*R.  In this way, 240 volts is 4 times 
worse to grab than 120 volts.  Lots of people in Europe die from electrocution.
     Now the water issue.  Pure water is a very poor conductor.  But there 
is no pure water out there except in chemistry lab.  Most water has ions 
that conduct electricity.  The more ions the more conduction.  Water in a 
lake will conduct better than one would think.  Seawater is a very good 
conductor.  Now, think about this (but DON'T EVEN THINK ABOUT DOING IT); if 
you had two metal containers, each connected to a 120 volt battery, one 
negative the other positive.  Now if the containers were filled with water 
from a lake and you placed a hand in each even without touching the metal 
you might be electrocuted.  This is due to the low resistance that is 
linking your arms to the source.  The contact area is large, much larger 
than the metal rod you could have grabbed onto.  Now if you fill the two 
metal containers with seawater you have a massive problem.  You will need a 
standard will, not a living will.
     One of the concerns that I have with my own submarine is the fact that 
I have 36 volts inside my hull.  If my sub flooded this could be a serious 
problem especially if in the ocean.  I would in no way want to be part of a 
36 volt or even a 24 volt circuit inside a flooded sub.  There are some 
precautions that can be taken but I have not taken them all.  I will admit.
     One last thought.  I recently saw on some TV show a reenactment of a 
near electrocution where this kid jumped off in a lake from a pier and 
suddenly stopped moving.  The problem was a 120 volt line hanging into the 
water supplying power to a pier light.  I seem to remember another person 
jumping into the water and having the same problem.  They got the power off 
and I believe both lived.  Had that been a saltwater scenario they would 
have probably died.  Killed by low resistance!!!

Gary Boucher


>I guess the point I'am trying to make is that 120v is  an arbitrary figure
>without the all important amperage figure.  I have personally held onto 120v
>from a wall socket without ill effect other than a vibration throughout my
>arm up to my shoulder.  Admittedly, the first time was a 'shocking'
>experience, but curiousity soon took hold.
>I once took a 1-year Vocational course in Heating and Air Conditioning.  The
>instructer demonstrated his ability to withstand a 120v shock by holding
>onto the bare wires of an extension cord while a student plugged it in.  He
>jerked momentarily, but was instantly able to assure us that little
>discomfort was present.
>Oh yes, 3-phase watch-out! Especially 440.  It will kill you instantly!
>No, 120v is little to worry about really so long as you isolate the grounds,
>and pay attention to the amperage.