what is sufficient for fatal electric shock.
ank_gl said:
oh man, don't talk about it. ever got a shock while doing arc welding?? like 45 volts and 80 Amps. now that's a jolt
ank_gl, there's some stuff you need to learn about voltage, current, and what's dangerous.
strictly speaking, it's current that's the mechanism that kills you and what organs that current passes through. all you need is about 1/4 amp at the right place (like through your chest), and your heart is stopped.
but you still get to apply ohms law and you need a sufficient voltage to force a sufficient amount of current through your body which has varing amount of resistance (depending on how sweaty the points of contact are, among other things).
i didn't think an arc welder had even 45 volts. i thought it was about half that. when i was in high school shop, i laid my hands on both contacts and did not get shocked. if the voltage is not there, it doesn't matter if it has 80 amps to back it up. it's a lot like a car battery. those suckers need to deliver hundreds of amps to start the car. i would easily dare to soak my hands in saline and grab both battery posts and very little of those hundreds of amps will flow through me. probably less than a couple mA. i probably wouldn't even feel it.
on the other end are devices such as electric fence controllers that anyone whose been around livestock (for me it was a dairy farm) is familiar with. now those controllers want to deliver enough current to the cow's nose to communicate it means business to the cow, it needs to do it under conditions that are wet or dry where there is a great variation in the resistance of the ground that the cow is standing on which is the return path of the electric current. on top of that, if the ground is moist (with less resistance), they don't want to kill the cow or, worse yet, the farmer or the farmer's kid or the kid of some guest. so how do they do that?? how can this electric fence, under wet or dry conditions, consistently deliver a few solid milliamps that tells the cow to back off, might put the farmer's guest's kid on his butt, but not kill either? here is a case where there is a lot of voltage (i think several hundred volts), but deliberately limited current. they deliberately put a large resistance (much larger than the variation of resistance in the closed loop connection) in series with the high voltage so that a consistent amount of current is delivered to whatever touches it. (that resistance is in the actual windings of the step-up transformer in the controller, so it's impossible to short circuit that series resistance.) they also pulse the electrical "signal" applied to the fence so that one can let go, in case the grabbed the wire. it's not dangerous to human or beast, but it *is* to small birds. i have seen the carcass of small birds that landed on the fence (no problem here, just like on high wires) and hopped over to the little steel fence post driven into the ground, and then they pecked at the post (across the little white insulator supporting the fence wire). fried that little sparrow's brain and the bird was just stuck there.
now power systems for home and industry have nearly unlimited current. in EE class, we call that an "ideal voltage source", one that will maintain a fixed voltage no matter how much current it dishes out. if the voltage is high enough and you touch that, unlike the electric fence controller, there is nothing except a 20 amp circuit breaker to limit the current. you probably will not draw 20 amps, but the 5 amps you do draw is easily enough to send you to the next plane of existence.
BTW, for U.S. states that are still barbaric enough to impose death by electrocution upon human beings, the voltage they use can vary (with a controller) between 500 and 2500 volts and it's backed up by 8 or 10 amps. the path is from the crown of the head to one calf (or both calves, in the case of, i think Tennessee) of the leg. they start out with the voltage cranked up to max to insure that the brain is just totally not thinking, but after 30 seconds, they back down to the min so that, without grossing everybody out, they can kinda "cook" the victim sufficiently that there is guaranteed fatal organ damage throughout and just ain't no way that the victim can conceivably recover. pretty ghastly science.
. but didnt gave the 45 volt thing much thought:shy:
. anyways its clear to me now.:shy:. duh i m stupid. i am feeling embarrassed:shy::shy:
