I'm Referencing: Foundations of Electromagnetic Theory - 4th Edition by Reitz Here's where I'm struggling: Then take a look @ this crude diagram of a circuit I've drawn. A voltmeter probe marked P (red) is moving along the circuit (red arrow), while the black probe remains stationary. Then would the reading in Voltmeter change? According to the quote, it should. Because assume the the two probes started @ one end of the battery's terminal. Then, the probe P, would end up @ the opposite terminal after its travel around the circuit, thus V = 0, should change into V = V_0. Is this correct?