About any frequency AC is dangerous/lethal if it goes through heart and current is 50mA or more.halcyon wrote:As for kills, in humans, it's the combination of through current (not on skin, but through the heart) at 50-60Hz that kills. The frequenc...
When missing heart internal burns are danger.
Also DC becomes dangerous if current is high enough but danger is mostly from burns.
You can't get hit by 100A from car battery because voltage is way too low. In fact current stays so low that you don't even feel it.slipknottin wrote:It is both true that you can get hit by 10,000+ volts (static, car distributor, taser) and not be killed, and that you can be hit by 100 amps (car battery) and not be killed.
Current goes through route of least resistance so sweaty skin can prevent current going to inside body. Exception to this comes from lightning whose very high voltage can make it go through nearly anything in its path/select less logical route.
Blood conducts electricity relatively "well" so current tends to go through blood vessels after penetrating skin. That's also what makes current going from one arm to other arm very dangerous. (it puts heart into route of current)
That's why electrician might have other hand in pocket while doing something.
Easy!peteamer wrote:Please don't ask me to explain how 1 Leg of 440V (Tri phase?...) becomes 220-240, it was 20+ years ago it was explained, it phased me out at the time and I've slept since then...
There's 240V between every phase and ground but because phases are in 120 degree phaseshift against each others voltage between two phases is 440V.
That symmetrical phaseshift between phases makes also ground/neutral unnecessary in case of symmetric three phase loads. (like motors)
It's all plain vector calculations.
This is also where different three phase configurations come into play, if three phase load is connected to Y/"star" configuration voltage affecting phase loads is phase to ground (240V in UK), in case of delta configuration voltage affecting to phase loads is that between two phase wires. (440V) For example in case of most common three phase loads, electric motors, that can be used for lowering spin-up surge (slowly/non-rotating motor has only resistive component left meaning it's nearly short circuit) by first connecting motor into star configuration and then changing it to delta configuration when spin-up is over.
US again uses system with two phases in 180 degree phaseshifts (opposite phase) meaning voltage between those two phase wires is double that of phase to ground.
http://en.wikipedia.org/wiki/Split_phase
http://en.wikipedia.org/wiki/Polyphase_system
http://en.wikipedia.org/wiki/Three-phase_electric_power
Calculating asymmetric three phase loads with reactive components and without neutral wire... that's where the fun begins!
... That's not what 'easy' means in England!! ..... 
