Let's say you have a wire connected to a device that you can switch between high-voltage and ground voltage. The wire is not connected to anything on the other end. You're observing the voltage in two places: one (#1 in the pic) very close to the device and one (#2 in the pic) at the far end of the wire. The wire has some load capacitance, so between the time the voltage toggles from low to high or high to low and the time that the wire is uniformly "pressurized", #1 and #2 will have different readings since the signal does not propagate instantaneously.
My question is this: would the voltage change propagate down the wire as a "sharp line", where at some point in time #1 would be close to high and #2 would be close to low? Or would #1 and #2 rise/fall more or less in tandem with just a tiny delay between the two?