To determine the potential difference between points $A$ and $B$, one must analyze the circuit diagram (not visible in the prompt). In typical questions of this type involving a p-n junction, one must first determine if the diode is forward or reverse-biased. If the diode is reverse-biased and ideal, it acts as an open switch (infinite resistance), meaning no current flows through the circuit. Consequently, there is no potential drop across any series resistors, and the entire source voltage appears across the open terminals (points $A$ and $B$). Assuming the applied source voltage is $10\text{ V}$, the potential difference between $A$ and $B$ will be exactly $10\text{ V}$.