Question

The following figure which is given is the potential barrier across a P-N junction, when no battery is connected across the junction:

A. 1 and 3 both correspond to forward bias of junction
B. 3 correspond to forward bias of junction and 1 corresponding to reverse bias of junction
C. 1 corresponds to forward bias and 3 corresponds to reverse bias of the junction.
D. 3 and 1 both correspond to reverse bias of junction.

Answer 1

Hint: This question is about p-n-p Junction from the chapter of semiconductors. In this question there is a graph given to us which is of stopping potential also known as the potential barrier. We have to analyze the different potential barrier values and find the biasing in the circuit of the junction.

Complete step by step answer:
When a P-N-P junction is forward biased it opposes the potential barrier, and the potential barrier is reduced and the current in the circuit is more. This is because the potential at both sides of the potential barrier is opposite as the concentration of charges naturally. Therefore, the charges attract and the value decreases.
When a P-N-P junction is reverse biased, it supports the potential barrier and increases its value, resulting in the current in the circuit is very less and almost negligible. This is because the potential at both sides of the potential barrier is the same as the concentration of charges naturally. Therefore, the charges repel and the value increases.
Hence, we can say that in forward biasing of the P-N-P junction the value of the potential barrier is less, and when a P-N-P junction is Reverse biased the value of the potential barrier is the most.
Now when we see the graph, the potential barrier number 1 has the largest value; therefore, it should be of the forward biasing of the circuit.
And when we see the potential barrier number 3 it is of the least value hence it should be of the reverse biasing of the circuit.

Thus, the correct option is (C).

Note:
This is a kind of question in which understanding of the biasing process of the semiconductors is very important. Also, students are able to see and visualize the graph of the potential barrier and the greater and lesser values of it and the reason behind those values. If all of these are kept in mind the students can easily answer these kinds of questions.