"blackboab" wrote in message
oups.com...
The LIVE and NEUTRAL wires are both passing current and the current is
reversing at 50 times a second so that they swap over the roles of
positive and negative.

Yep

can i get electrocuted by holding the NEUTRAL ?

You shouldnt do, becasue back at the electrcity sub station the nuteral is
connected to the earth (and in the brown stuff outside) so everything is
connected to nutral all the time.

a circuit only needs two wires to be complete.

so how does the third wire - ground - fit in the circuit ?

The ground, or earth wire is only there for protection, if there was a fault
in an appliance where the live or the neutral wire somehow came into contact
with the metal casing of something, the current will travel down this wire
instead of down the neutral wire.
Now, if the wire that has become connected to the metal casing of the
appliance is the Live, this is effectively shorting the live to the neutral,
causing a lot of current to flow (because neutral is connected to the earth)
so your fuse or little MCB (Circuit breaker) will blow/trip.

Also, if you have an RCD, this checks the current going out of the Live, and
returning back via the Neutral, if there is an imbalance (because some is
going to earth, maybe through a person, or the earth wire etc.) then the RCD
trips.

Sparks...