Heres something, if you dont have a non touch tester, try this put a regular flouresent bulb upto the romex (not cfl) dont touch the metal ends of bulb to the end of the romex wire. The bulb will glow ever so lightly in a darken room, because the emf in the wire will excite the photons in the gas in the tube.
Interesting, I did not know this. Makes sense though, I did discover as a kid that static electricity does make it glow, too. Move a plastic bag near one in the dark, it's pretty fun.