Please see the attached illustration. This is clearly an open circuit. The voltage source is producing a voltage at some amplitude and frequency. If one were to measure with an oscilloscope the potential difference at the point where the mouse pointer is with respect to the ground, what would be observed? Or, to simplify the question (you don't really even need the resistor there) -- if one were to measure the potential difference between one pole of an AC voltage source and ground, would anything be observed, or would it be a flat line? -Thanks.