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Electrical Safety Reminder

Watching the video, it appears to my keenly amateur sense of observation that the dude was walking on the rounded surface of the roof and was merely reaching for the line as a method of increasing his stability.

I agree. I believe it's quite a normal and everyday thing in some regions of India for people to cling to the outsides of vehicles for travel as that way they don't have to pay fares. That would be my first guess what is going on here, but with the man totally unaware of the danger he was in.
 
*shrug* Dude felt it for waaay less than a second if at all.. Rough on surviving family members if there were any.
 
I wonder about that. His head wasn't in the direct circuit path. One can only hope that with that much raw power going through him, eddy currents alone would instantly depolarize his neurons.
 
Meredith,

Voltage don't kill it is Amps that does the frying!!

Regular static shocks from walking across carpet can be in the tens of thousands of volts but less than 1 milliampre.

Think of Voltage as Pressure and Amps as Flow.

I thought wattage was more important. Watt = Volts x Amps
 
I wonder about that. His head wasn't in the direct circuit path. One can only hope that with that much raw power going through him, eddy currents alone would instantly depolarize his neurons.

I'll agree there, I think the damage would outrun the neurons being able to send signals.

At that kind of voltage, wierd current paths are virtually addured. Since the brain is marginally higher than muscle in water content, I suspect it was in the path of the initial shock.

I *think* the second shock was cranium on cable. Again, hard to tell from one angle and no depth perception. If Darwin hadn't reigned supreme before that point, Charles took him then to be certain.

In any case, ohms law and watts law says some serious electricity passed through dudes head since his hair seems to be smouldering or actually burning in the last bit of the video. This was low frequency stuff, so the "skin effect" that happens with high frequency sources like Tesla coils wouldn't keep the current close to the surface.
 
Meredith,

Voltage don't kill it is Amps that does the frying!!

Regular static shocks from walking across carpet can be in the tens of thousands of volts but less than 1 milliampre.

Think of Voltage as Pressure and Amps as Flow.

I thought wattage was more important. Watt = Volts x Amps

Well yes, but it's actually voltage drop x Amps. The more resistance the body offers, the greater the voltage drop.

If he was a perfect conductor, there would be zero voltage drop = he's dissipating zero watts = no damage.

If he were a perfect insulator, there would be no Amps = he's dissipating zero watts = no damage.

It's the stuff that's partially conductive that is dissipates the most watts. Human bodies are partially conductive. Since the train was a far better conductor (<1ohm), the voltage drop across the boy would have been pretty much as high as the voltage rating of the power line.

Also, it isn't as simple as resistance when you're dealing with AC. Replace Resistance with Impedance.

Static shocks from clothing are relatively harmless because there is negligible Charge. This limits the power dissipation to a split second of discharge time : Time = Charge / Amps. So the discharge event is over before a neuron has time to fire, which is around 1/20000 th of a second.
 
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I refuse to discuss the inductive or capacitive reactance of a human head. The DC model works well enough for the purpose of "Don't touch a frakkin' live wire!", methinks.
 
Meredith,

Voltage don't kill it is Amps that does the frying!!

Regular static shocks from walking across carpet can be in the tens of thousands of volts but less than 1 milliampre.

Think of Voltage as Pressure and Amps as Flow.
I thought wattage was more important. Watt = Volts x Amps

Well yes, but it's actually voltage drop x Amps. The more resistance the body offers, the greater the voltage drop.

If he was a perfect conductor, there would be zero voltage drop = he's dissipating zero watts = no damage.

If he were a perfect insulator, there would be no Amps = he's dissipating zero watts = no damage.

It's the stuff that's partially conductive that is dissipates the most watts. Human bodies are partially conductive. Since the train was a far better conductor (<1ohm), the voltage drop across the boy would have been pretty much as high as the voltage rating of the power line.

Also, it isn't as simple as resistance when you're dealing with AC. Replace Resistance with Impedance.

Static shocks from clothing are relatively harmless because there is negligible Charge. This limits the power dissipation to a split second of discharge time : Time = Charge / Amps. So the discharge event is over before a neuron has time to fire, which is around 1/20000 th of a second.

We used to have a lot of fun in school making resistors and capacitors explode, kinda like this dude.... :)
 
I refuse to discuss the inductive or capacitive reactance of a human head. The DC model works well enough for the purpose of "Don't touch a frakkin' live wire!", methinks.

I know, I'm just providing some opportunities for extra study. :p
 
Well, that was pretty horrible.

It's fairly obvious that the effects of 25kV at such a high current would include instant ventricular fibrillation (which is deadly on its own within seconds), and would also likely cause all the neurons in the brain and CNS to fire in a random uncontrolled way which is not particularly compatible with conscious thought (if his muscles weren't already being fried by the aforementioned electricity we'd probably see him seizing).

Therefore I suspect the poor chap didn't even have time to realise his mistake before his head hit the carriage :borg:

More likely passed through him than you'd get strapped in to an electric chair :borg:
 
It only takes 5 mili amps to kill you, and that can be found in a capacitor in your TV.

I've never heard a figure that low. I've heard figures from 15-50mA.

This deal about how much current it takes to kill is often misunderstood - even by people who work in electrical fields. I've lost count of how many people I've known who thought a car battery can kill you because it can put out hundreds of amps. Usually, they don't stop to consider that even a AAA cell can put out the 50mA that will definitely kill.

If you grab across a power source you will get the full voltage but the amount of current passing through you is found by Ohm's Law. Divide voltage by body resistance in ohms to find current. Skin resistance (which is a non-factor when high-voltage arcing occurs) is typically better than 100,000 ohms. You get just over a tenth of a milliamp from the car battery.

The bottom line is that while it is current that kills, current can only flow with enough voltage to push it. That's why car batteries are left on the shelves at Wall Mart with exposed terminals.
 
Actually most automotive batteries have a cap on at least one terminal. It's no so much electrocution risk they're concerned with, but have you ever seen a wrench dropped across a car battery terminals??? :)

As for those low currents being lethal. Technicaly they can, but getting the current flowing where it could do that damage is the trick to it.

a 9 volt battery could kill, but geting the current to flow from in such a way that it crosses the cardiac muscle? Well, you see, there was an eastbound truck loaded with 9 volt batteries & travelling at 107 miles per hour, and Joe Heartshock is riding a unicycle westbound at 3 miles per hour...
 
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