Question

The potentials are applied to the four p-n junctions as shown below. The forward biased p-n junctions are:

• A. (A), (B), and (D) only
• B. (A), (B), and (C) only
• C. (B), (C), and (D) only
• D. (A), (C), and (D) only

Answer 1

The Correct Option is C

To determine which p-n junctions are forward biased, we analyze the potential connections:

Characteristics of forward bias:

• Positive terminal connected to p-side
• Negative terminal connected to n-side
• Applied voltage overcomes built-in potential

Analysis of each junction:

Junction	Connection	Bias Type
(A)	-ve to p, +ve to n	Reverse
(B)	+ve to p, -ve to n	Forward
(C)	+ve to p, -ve to n	Forward
(D)	+ve to p, -ve to n	Forward

The forward biased junctions are: (B), (C) and (D) only

Note: Junction (A) is reverse biased as it has opposite connections.

Answer 2

For a p-n junction to be forward biased, the potential on the p-side must be higher than the potential on the n-side.

Let’s examine each configuration:- 

Configuration (A): The p-side is at −5 V and the n-side
is at −3 V. Since the n-side is at a higher potential, this junction is reverse-biased.
Configuration (B): The p-side is at 0 V and the n-side is at −3 V. Since the p-side is at a higher potential, this junction is forward-biased.
Configuration (C): The p-side is at 7 V and the n-side is at 3 V. Since the p-side is at a higher potential, this junction is forward-biased.
Configuration (D): The p-side is at −10 V and the n-side is at −20 V. Since the p-side is at a higher potential, this junction is forward-biased.

Thus, the forward-biased junctions are (B), (C), and (D).