[QUOTE=abel29a]
I resently saw a Mythbuster episode where they tested the old toaster in the baththub clichee - and unsurprisingly they concluded that this was indeed lethal for anyone unlucky enough to be in the bathtub at the time.
[/QUOTE]
I didn’t see this episode. Wish I had. Maybe it will come on a repeat soon.
Anyway, Mythbusters usually tends to test the “fatality” of an electrical situation by measuring the current flow. If it’s above a certain level, then it is fatal. If not, it’s safe. That’s fair enough to determine if something is dangerous or not, but what really happens is a lot more complex than that.
Electricity kills you in generally one of two ways. It either cooks you to death (literally) or it screws up your heartbeat. It takes a lot of energy to cook you to death, but if you’ve got this much energy, the shock is almost always fatal. The electric chair is a good example of how to cook someone to death.
It takes a surprisingly small amount of energy to screw up your heartbeat, and it is this small current level that Mythbusters generally tests to. But, this is a lot less guarnateed. At these current levels, the electricity might kill you, or it might not. A lot of it depends on exactly what part of your heart’s rhythm it happens to be in when you get shocked. Your heart is more sensitive to being thrown out of whack at some points in your heartbeat than others, which is why it’s a lot more random.
The thing about the low level shock is that the current has to flow through your heart to cause problems. If you are sitting in a tub, and the electricity flows through your legs, it’s no big deal. It might not be very comfortable, but it wont’ kill you. As soon as you reach for the toaster, though, you get your arm involved, and your arm is connected to your chest, and as soon as the current flows through your chest then you really have problems. A shock that barely tingles is more than capable of stopping your heart.
I don’t know what the probabilities are, but people get shocked all the time and don’t die from it. Of course, a few do die, which is why we have safety rules and such.
[QUOTE=abel29a]
However, this got me thinking - how big a body of water could you electrocute in this manner? If I was, say, in one end of a largish swimming pool and some evildoer dropped a toaster or other appliance in the other end - what size would the pool have to be to let me stand a reasonable chance of surviving?
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As long as you kept your arms and chest up out of the water, you’d have a reasonable chance of surviving in a bathtub. If you get your chest involved in the shock, then you’d probably need to be a couple yards or so away from the toaster to have a good chance of survival. For an average sized back yard swimming pool, you’d be pretty safe when the Evil Bad Guy drops the toaster in the other end.
[QUOTE=abel29a]
Another scenario - a flooded area, with powerlines falling down and for some reason the current is not cut but continues to flow between the severed ends of the line. How close to this could one swim without getting electrocuted? I’ve seen footage of people swimming in flooded areas with broken powerlines giving of sparks in the water 100 meters away, how lucky were these people that they werent electrocuted?
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100 meters is pretty far. Power lines are a lot higher voltage than the lines inside your house, but even so the chances of them getting electrocuted at that distance are pretty small.
Power lines are particularly dangerous because they have circuits which automatically shut off the electricity when there is a fault, and other circuits callled reclosers which periodically try to reconnect the line. The reclosers typically try to open the line again a few times quickly, then once after say fifteen seconds, then once after a couple of minutes, and then they give up. You see sparks and wade out into the water, but you don’t feel a shock because at that point the line is dead. You think it’s safe now, so you keep wading out. Then the two minutes goes by and the reclosers connect the line, and a huge current flows through the water (and you). The line shuts back off because the line is still down and shorting out, but you end up dead because of the momentary current.
