My grandpa asked me a question regarding the signal coming out of a power outlet. We know that the ground hole is always ground, and that between the two power holes there is a 120 Hz sine wave signal. However, I don't know how exactly is that signal sent. That is to say, what are the node voltages at the holes? Is one hole giving the whole range of voltages while the other just stays at ground level (figure 1)? Or does each hole provide a staggered half-rectified sine wave (figure 2)? Thanks in advance for any help.