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In article ,
says...

"bill" wrote in message
news:MPG.1b09eda2ef2138ea98970e@localhost...
snip
Voltage doen't kill you, current does. You get hit a lot of
voltage when zapped with static electricity, but very little
current.

Yes but they dont use static electricity in electric fences, do they?




Electricity is electricity. Lightning is static electricty, but I
wouldn't want to get hit with it.

No, there's a difference. A static charge of 1000v will (in most cases)
dissipate so quick you barely hear the snap, where 1000v ac or dc will kill
you more than likely. Now that I think of it some, it may be that they *do*
use static electricity for fences. Looked up electric fence on the
internet. What I read doesnt explicitely say static charge, but they are
talking about powering it with a low voltage battery so that does kind of
imply a short lived charge.




Your static charge is DC. It's the same as the charge stored in a
capacitor. It just happens to be created by friction instead of a
battery or other mechanism. The zap you feel when you get charged
up shuffling across a carpet then touching a door knob is just the
electrons flowing from you to the door knob hence DC. It doesn't
kill you because there isn't a lot of current flow for a long
period of time.

"Ampere. The unit of electrical current. Also milliamp (one
thousandth of an amp) and microamp (one millionth of an amp). One
amp corresponds to the flow of about 6 x 1018 electrons per
second."

So 1000v that only produces current flow for a millisecond is
going to be felt, but that's about it because as soon as the
current starts flowing there's nothing to keep it flowing and the
voltage drops quickly. When you get hit with 1000v with a power
source behind it that can keep the current flowing with out the
voltage dropping your in deep doodoo.

For the sake of argument, lets say your body equals 100 ohms of
impedance: 1000v /100 ohms = 10 amps but since amps are a
function of current over time and current flowed only for 1
millisecond you have to divide 10 amps by 1000 and get 10 milliamp
equivalent. Enough to get your attention for sure. But rarely if
ever fatal.

See:
http://www.t2.unh.edu/spring99/pg4.html

for the effects of rising levels of current flow.

The fences probably use a capactive discharge circuit.


Bill