Possible For Floating House Wire To Pick Up Low Volt. Via Inductive Coupling, Or... ?

["Robert11" <rgsrose@xxxxxxxxx>]

Hello:

Have a length of 3 conductor (and Gnd. wire) No. 14 AWG running around my
house.
Would like to use the red, third conductor, to interconnect some wired-in
smoke
alarms.

This red wire is at present, to the best of my knowlege, totally floating.
Believe that there is nothing hooked to it now.

(but, it is hard to trace totally, and there might possibly be "something"
connected to it  that I am unaware of ?)

Anyway, my question is:

Assuming that it really is totally floating, how likely, or possible, would
it be
for this wire to pick up, e.g. 2 V AC, via inductive coupling, RFI, or... ?

I ask this because I measure 2 V AC on it (relative to the white neutral),
which I cannot account for.

Thanks,
B.