Wow, a thread with fact-to-myth ratio of 1:10
OK here it goes:
- The reason for the 'voltage divide' between North America and Europe has little to do with safety: In the 1950-1960s, most of Europe went through a conversion process from 110/120V to 220/240V, as transmission of electricity at a higher voltage level is more efficient. However, US decided not to, primarily because of the associated costs, as all existing electrical devices would have needed to be replaced (some say that a typical US household would have had far more appliances back then).
- Voltage levels up to approx. 36V AC - 50V DC are, generally, considered safe for humans. So by touching the terminals of a 12V DC car battery with any part(s) of your body, you will not feel anything.
- Voltage levels exceeding the above are dangerous and may be lethal (provided that the device is capable of generating sufficient level of current).
- Standard circuit breakers will not protect a human from receiving an electric shock.
- Earth Leakage Circuit Breakers (known as Ground Fault Circuit Interrupters in North America) offer limited protection in certain specific situations. They would be useless in an aircraft setting, so you won't find them there.