Physics - Semiconductors Question with Solution | TestHub

A p-n junction diode is said to be forward-biased when its p-side (anode) is at a higher potential than its n-side (cathode), i.e., $V_p>V_n$.

Let us check the potentials for each given figure:
In figure (A), $V_p=0\text{ V}$ and $V_n=-4\text{ V}$. Since $0\text{ V}>-4\text{ V}$, the diode is forward-biased.
In figure (B), $V_p=-4\text{ V}$ and $V_n=-3\text{ V}$. Since $-4\text{ V}<-3\text{ V}$, the diode is reverse-biased.
In figure (C), $V_p=-2\text{ V}$ and $V_n=+2\text{ V}$. Since $-2\text{ V}<+2\text{ V}$, the diode is reverse-biased.
In figure (D), $V_p=3\text{ V}$ and $V_n=5\text{ V}$. Since $3\text{ V}<5\text{ V}$, the diode is reverse-biased.

Therefore, only figure (A) represents a forward-biased diode.

Answer: A