"Charles Schuler" wrote in message
The neutral (white) is a return ... it carries the same current as the hot
wire (black). The ground wire is a non current-carrying safety wire
(often
bare copper). The purpose of the ground wire is to reduce voltages in the
case of lightning or an accident (wires falling across other wires outside
of your home and raising the voltage with respect to ground to a dangerous
level). The ground wire only conducts current in the case of a fault.
Ground fault circuit interrupters need the ground wire to detect such
faults
and open the circuit when they occur.

I believe that GFIs are often recommended in cases where there
is no ground for safety. They do not need a ground AFAIN.

Bob