A voltmeter measures the difference in electric potential from one probe to the other. A voltmeter reading of 9 means that the red probe is touching a point in the circuit where the potential is 9 V higher than the point the black probe is touching. Sometimes we refer to voltage as the potential difference, since rather than telling us the value at one point it tells us about the difference between two points. Each of the circles where the wires and/or batteries connect is a point where you can touch the probe. First switch sides with the red and black probes. Cross them over so that they touch the batteries on the opposite side from your previous measurement. What changes