Neutral wires are present in 120V circuits as well, yes neutral and ground
busses are bonded together in the panel, but the white wire is still
called neutral though it carries the full return current. A white wire can
be hot if used in a switch drop or to a 240v appliance receptacle but in
that case there should be a band of black or red tape around it to mark it
as such, though in most houses I've worked on they've skipped that.

A lot of people refer to the white as a neutral, but offically in the NEC is
referred to as an "identified" conductor.

A neutral is only present in a 240 v or higher branch circuit or feeder. (I
think that's where a lot of confusion comes in as the potential between a
240 volt leg and the neutral is 120 volts, however that's not a branch
circuit in and of itself). Because a neutral carries only an unbalanced
load, it's allowed to be reduced in size from the ungrounded phase
conductors. See 220.61 where the NEC talks about how to calculate the
unbalanced load on a neutral. A grounded white wire in a 120 volt circuit
always carries the full load of the circuit and is sized the same as an
ungrounded conductor.

I pulled this off of Mike Holt's website (read carefully, the 2-wire circuit
in the 2nd para is a standard 120 volt circuit):
Neutral Conductor. The IEEE dictionary defines a neutral conductor as the
conductor with an equal potential difference between it and

the other output conductors of a 3- or 4-wire system. Therefore, a neutral
conductor is the white/gray wire of a 3-wire single-phase

120/240V system, or of a 4-wire three-phase 120/208V or 277/480V system.

Since a neutral conductor must have equal potential between it and all
ungrounded conductors in a 3- or 4-wire system, the white wire

of a 2-wire circuit, and the white wire from a 4-wire three-phase 120/240V
delta-connected system are not neutral conductors-they're

grounded conductors.


Anyway, I believe that the white IS called a neutral in the UK, but not here
in the US (not by the NEC anyways).