Question

In which of the following figures, diode is reverse biased?

• A. Figure (1)
• B. Figure (2)
• C. Figure (3)
• D. Figure (4)

Hint:

Always treat "less negative" as a higher potential. For example, \(-10\text{ V}\) is at a higher potential than \(-20\text{ V}\). If the arrow of the diode (p-side) points towards a higher potential, it's reverse biased.

Answer 1

The Correct Option is B

Step 1: Understanding the Question:
We need to determine which circuit configuration results in a reverse-biased diode by comparing the potentials of the p-side and n-side.
Step 3: Detailed Explanation:
A diode is:
- Forward biased if the potential of the p-side (\( V_P \)) is higher than the potential of the n-side (\( V_N \)), i.e., \( V_P>V_N \).
- Reverse biased if the potential of the p-side (\( V_P \)) is lower than the potential of the n-side (\( V_N \)), i.e., \( V_P<V_N \).
Let's analyze each case:
(1) \( V_P = 5\text{ V} \), \( V_N = 0\text{ V} \) (grounded). \( V_P>V_N \Rightarrow \) Forward biased.
(2) \( V_P = -20\text{ V} \), \( V_N = -10\text{ V} \). Since \(-20<-10\), \( V_P<V_N \Rightarrow \) Reverse biased.
(3) \( V_P = 15\text{ V} \), \( V_N = 10\text{ V} \). \( V_P>V_N \Rightarrow \) Forward biased.
(4) \( V_P = 20\text{ V} \), \( V_N = -5\text{ V} \). \( V_P>V_N \Rightarrow \) Forward biased.
Step 4: Final Answer:
In figure (2), the diode is reverse biased. This corresponds to option (2).