In the forward bias characteristics curve, a diode appears as:
A) An OFF switch.
B) A high resistance
C) An ON switch.
D) A capacitor.

Hint: The p-n junction is a junction between a p-type semiconductor and an n-type semiconductor. A p-n junction cannot be formed just by placing a p-type semiconductor in contact with an n-type semiconductor. There are a number of ways for constructing a p-n junction. One of the common methods is alloying.

Complete step by step answer:
A p-n junction is said to be biased if it is connected across a battery. There are two types of biasing.
1. Forward biasing
2. Reverse biasing
Forward biasing: When p-type is connected to the positive terminal of the battery and n-type is connected to the negative terminal of the battery, then it is said to be forward-biased.
The resulting field is therefore weakened and at the junction the barrier height is reduced. Once the forward voltage removes the potential barrier, the resistance of the junction becomes almost zero and hence the current flows through the circuit. A diode thus appears as an ON switch.
Therefore, option(C) is the correct answer.

Additional information:
As soon as a p-n junction is formed, n-type material electrons diffuse into p-type materials and fill some of the holes there. At the same time period, holes from p-type materials diffuse into the n-type material and are filled by electrons. This migration of charge carriers results in n section gains a positive charge and a p- section a negative charge. These two layers of positive and negative charges create a depletion region or layer.

Note: When p-type is connected to the negative terminal of the battery and n-type is connected to the positive terminal of the battery, then the set-up is said to be reverse biased. P-n junction behaves like a closed switch when it is forward biased.