Re: On-line Dog License Application (with questionnaire)


"Rocky" <3dogs@xxxxxxxxxxxxx> wrote in message
news:Fri999ED03E5A8CEaustralianshepherdca@xxxxxxxxxxxxxxxx
"Paul E. Schoen" <pstech@xxxxxxxxx> said in
rec.pets.dogs.behavior:

High current at low voltage is fairly safe,

Backwards.


Certainly if the high current is going through your body, especially your
heart, it is not safe. Even 10 mA at 60 Hz into the heart can cause
fibrillation and death. But I'm talking about the current going through a
low impedance like a circuit breaker, which requires only about the same
voltage as a car battery. It takes a certain amount of voltage to deliver a
dangerous current into the body, and it varies greatly depending on skin
resistance and location of the electrodes. Body resistance is typically
about 10 kOhms from one hand to the other, so 120 VAC would produce 12 mA.
However, the resistance can drop due to sweating, and the current can
quickly reach dangerous levels of 20-50 mA.

Higher voltages cause proportionally more current, so they are more
dangerous (unless greatly limited in current). Above 5000 volts, which is
technically the lower threshold of "high voltage", there is the additional
danger that merely being close to the voltage source can cause it to arc
through the air, so you don't even need to touch it. Typical air breakdown
is about 10 kV per inch. You also have electrostatic fields, which are what
cause your hair to stand on end, and corona, which is a visible effect,
particularly on sharp pointed metallic objects. You can check the Wiki or
do more scholarly research to learn more. High voltage is not my area of
expertise. I know enough to stay the hell away from it. It is scary enough
working with 480 or 600 VAC, which is technically "low voltage", but
capable of immense damage as can be seen in the 480 VAC blast on
http://electricsubstationsafety.com/photo5.html.

The low voltage that I consider safe is up to about 24 VAC. Telephone
circuits operate on 48 VDC, which is also considered safe, but it can give
you a nasty shock. Being DC, and limited to about 20 mA, it is rarely
fatal, but the ring signal is about 100 VAC, which is enough to be
dangerous, although the 25 Hz is less likely than the "ideal" 50-60 Hz to
cause fibrillation.

Thus I refute your "backwards" comment. Make sure you know whereof you
speak. What you don't know *can* kill you!

Paul


.

Relevant Pages

  • Re: Re: Vintage electrical machines
    ... Voltage is the driving force ... particularly low impedance state such as when the skin is wet it only takes ... the path the current takes is fundamental to the danger, ... the heart is very dangerous but one across the hand for example is far less ...
    (uk.rec.engines.stationary)
  • Re: Vintage electrical machines
    ... Voltage is the driving force ... particularly low impedance state such as when the skin is wet it only takes ... the path the current takes is fundamental to the danger, ... the heart is very dangerous but one across the hand for example is far less ...
    (uk.rec.engines.stationary)
  • EE and JScript Thread in Dogs NG
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    (sci.electronics.design)
  • Re: Transformer question; safety
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  • Re: Electrify Vehicle Body?
    ... A small current that disturbes your heart rhythm is all thats needed. ... And once current gets into the body tissues, it tends to spread out so the current through any particular area far away from the point of contact with the external voltage source will be low. ... If you grab two wires, one in each hand and your hands are dry, it takes many times that voltage (and you'll feel pain before the current density in the chest cavity gets very high). ... You can't really say "a 12-volt car battery can't kill a person" because under some very odd circumstances it just *might* But its extraordinarily unlikely. ...
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