How many wires in a 110 volt circuit?

Answer 1

Usually there are 3 wires.
The Black wire or the "hot wire" this is connected to a circuit breaker or a fuse.
The White wire returns the electricity from the load like a light bulb, motor, etc. to the electric panel. Technically it is a current carrying ground wire and you can get a shock from it especially from a ballast from a fluorescent light.
The green or bare copper wire is the ground and is supposed to be non current carrying.
Older home and barns just have 2 wires, the oldest before ("romex" AKA type NM (nonmetalic)) is knob and tube.

Answer 2

A typical 110 volt circuit consists of three wires: one hot wire (usually black), one neutral wire (usually white), and one ground wire (usually green or bare copper).