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Peter[_14_]

On 4/6/2010 3:37 PM, wrote:
On Tue, 6 Apr 2010 12:03:40 -0700 (PDT),
wrote:

As for safety, I have never experienced a 120volt DC shock. Has
anyone? Is it less painful or harmful than 120v AC? I have no
idea.... I know that a 12VDC car battery can not shock a person, or
at least it's not noticable.

The great danger from power company AC (more so in the Northern Hemisphere than
in the rest of the world) is the 60 Hz frequency - which is close enough to your
heart muscle's pacemaker to throw you into ventricular fibrillation (which is
lethal unless defibrillated with a DC shock). Outside of the Northern
Hemisphere they tend to use 50 Hz, which is somewhat less dangerous because it
is less likely than 60 Hz to ruin your entire day!

AC shocks produce a sensation of intense vibration without a lot of motion in
your muscles, which can make it very easy to continue to hold on to whatever you
have touched that is conducting the shock. DC shocks produce a violent
contraction in the muscles, which if you are lucky will cause you to jerk away
from the conducting object. They both can be quite painful, depending upon the
amount of current and the duration of the shocks.

Don't believe that you cannot receive a really painful and/or injurious shock
from a car battery. It depends upon your resistance (are you full of
perspiration at the time you receive the shock or is your skin entirely intact
and dry). Car batteries can deliver a really nasty high amperage shock if the
resistance in the shock path is low and you can get really nasty burns from the
heat that can be generated.

The damage from a shock is related to the energy (watts) delivered which is the
product of the voltage and the current. The lower the resistance, the higher
the current (given a constant voltage).