Each part of this figure is a depiction of a PN diode as in part B of the previous figure. In part A the positive end of a battery is connected to the left end of the diode. The negative end of the battery is connected through a resistor to the right end of the diode. The depletion region is much wider than in part B of the previous figure. An electrical potential graph is shown above the diode. At the left end of the graph the curve starts out above the axis indicating a positive potential from the battery. It rises even higher reaching a peak just before the junction where it falls very quickly crossing zero at the junction and reaching a negative peak. It becomes less negative but does not reach zero at the right end of the diode. In part be the battery has been reversed so the negative is to the left end of the diode and the positive goes through the resistor to the right end. The depletion region is much narrower than in part B of figure 3.4 but there is still a small gap. The electrical potential graph starts out negative and slowly rises crossing zero before the depletion region begins and reaching a peak just before the junction. Then it falls crossing zero at the junction and quickly reaches a negative peak. Then it turns to go up and crosses zero a little to the right of the end of the depletion region and ends positive at the right end of the diode. In part C the depletion region has been reduced to zero. The graph begins at a more negative potential than in part B of this figure. It rises becoming almost horizontal near the junction but crosses zero at the junction and keeps going positive until it gets to the right end of the diode. End verbal description.