Good point Randy, for all of my home electrical work I choose to use the type of receptacle that has the clamp type of connection. You put the wire in the large hole and tighten the screw until the wire is clamped. These are more expensive but give the best connection of all. I’m not a residential electrician so time and money are not as important as safety.

This might help explain why there is voltage on the open wire. It is a very general description of how a transformer works. A transformer is basically two coils of wire wrapped around an iron core. The coil of wire that is connected to a voltage source produces a magnetic field. As the lines of magnetic force move across the second coil of wire they produce a voltage in it. The amount of voltage produced in the second wire is dependant on the number of turns of wire in each coil. Two wires laying next to each other will react in the same way. Because of the short lengths of the wires in your home and the distance between them the amount of energy transformed is very small. Your digital meter, while having a very high impedance, still places enough of a load on the open wire to pull the voltage down to 30 volts or so. While you are doing the measurement the open wire is really not open anymore. Your meter completes the circuit. The resistance in your body is much lower than that of your meter. If you were to touch the open wire and ground at the same time the voltage would drop down so far that you would not even feel it. All this only applies to AC systems. Also, you might have noticed that the 30 volts was not always there. For the first wire to pass a voltage to the second it must have a load on it to produce current. Without a load there would be no current and so no magnetic field. As the load goes up the strength of the magnetic field also goes up and the amount of energy transferred to the open wire goes up. Since your meter has a set impedance this would show up as the voltage measured going up as the load on the live wire goes up and vise versa. I hope this helps!