甚麼是回路電

return path:

in electric circuit. the return can using the neutral (black core/ blue core) or earth wire.
It form the complete circuit of the electric.
under ohm law V=IR,

all the electric must be form a one completed circuit. The current can be flow to the equipment.

If common circuit. subject to Live, Neutral...and CPC circuit protective conductor "Earth"

Heat generation. subject to below items:
less cable size (overload the cable)
laid on bad cooling area (fail to natural air cool)
many equipment used in same outlet..(overload)

Last..question...i don't understanding

什麼是飛機仔？