If you were to splice the wires on an ac power cord and measure the + and - signals would they look the same, or shifted 180 degrees? Or something different?? thanks!

 

It depends upon the AC you're looking at!
In the US, residential service is 120v/240v. There is L1, L2, and Neutral.
L1 and L2 are the opposite ends of a center tapped transformer, and Neutral is the center tap.

At the service panel, Neutral is tied to earth ground for safety.
At a typical 120v outlet, you'll have L1 or L2 (Hot), Neutral and Ground.
If you used Ground as a reference, you'd find very little difference between Neutral and Ground, and about 120v RMS between Hot and Ground. If you do find more than a few volts difference between neutral and ground, call an electrician.

In a 240v outlet (say for a dryer or other 240v appliance) you might just have L1, L2 and Ground. L1 and L2 are of equal amplitude and opposite in phase (180° apart).