Video 1.1i Extracellular Current Flow. Gray arrows represent current flow between the battery terminals. As the battery approaches the electrodes, the current flowing past the probes becomes greater, resulting in an increasing voltmeter reading. When the battery is to the left of the voltmeter, current flows from the positive probe to the negative probe, giving a positive reading. When the battery is to the right of the voltmeter, current flow past the probes is reversed, giving a negative reading. When the battery is between the probes, equal currents flow in opposite directions past the probes. Thus the probes are at the same potential and the reading is zero. (Drag the slider control to go through the video slowly.)