[SI-LIST] Re: threshold

Here's a couple more links for those interested:


http://www.kwantlen.bc.ca/electronics/eltn1111/edata/ElectricShock.pdf

http://www.chipcenter.com/eexpert/lkamm/lkamm021.html



-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] =
On
Behalf Of McCoy, Bart O.
Sent: Wednesday, July 30, 2003 9:38 AM
To: si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] Re: threshold


I'm no expert on this, but what I know I'll share:

The voltage/current at which we can "feel it" or "getting hurt" by it is
frequency dependent-- due to the physiology of the body, muscles, etc. =
How
*wonderful* that 60 hz is in probably the deadliest in our danger-zone
frequency band of 5 Hz - 500 Hz.   60 Hz is so potentially deadly
because it can cause muscle spasms/contraction that prevent you from
letting go of live voltage sources.   Also, unknown to many people,
lower voltages like the home 110 V or 220 V can be more deadly that=20
higer voltages (neglecting the tens of kV range) because the initial =
jolt of
lower voltage sources is not sufficient to knock you off of the source =
like
maybe 440 V is.

Typically, transient currents of >=3D 1 mA can be felt.   Whether or not
it's lethal depends on many factors, most importantly:   (1) the =
duration
of the pulse (5-15 kV & up to 1 A for around 1 microsecond for carpet =
static
discharge) and=20
(2) whether that current gets routed near the heart.   Currents as low =
as 40
mA, if they
pass through the heart for sufficient duration, can be lethal.   Carpet
static is
not lethal because of it's short duration and the capacity of the body =
to
absorb
the net quantity of charge injected (maybe 1A for 1 microsecond).  =20

Voltage and current are 2 different things-- the lethal potential of a=20
pure voltage source depends upon physiological factors that determine =
body
resistance.   Dry, dead skin can have 100 kOhms of resistance while wet
clammy palms can be as little as 100 ohms.   That, obviously, will have =
a=20
lot to do with the current that passes into your salty, good-conductor
nerves/blood/blood vessles.  =20

That is why good electricians forced to work on live circuits avoid =
sticking
BOTH hands in a live junction box at the same time-- it decreases the
chances


   - Bart McCoy




-----Original Message-----
From: Clewell, Craig [mailto:cclewell@xxxxxxxxxxxxxx]=20
Sent: Wednesday, July 30, 2003 7:55 AM
To: 'si-list@xxxxxxxxxxxxx'
Subject: [SI-LIST] Re: threshold


...that would depend on weather you are James Bond or an ordinary =
citizen.=20

However, this may help ~~> =
http://hypertextbook.com/facts/2000/JackHsu.shtml

=09
http://www.smud.org/safety/world/hurt/chart.html

-----Original Message-----
From: hariharan [mailto:hariharan@xxxxxxxxxxx]
Sent: Wednesday, July 30, 2003 8:44 AM
To: si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] threshold


what is the threshold  Voltage (V) and current (amps) beyond which human
beings can get hurt or feel it?

any idea...??




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