In which of the following figure the junction diode is reverse biased ?

Options

A.
B.
C.
D.

Explanation

To determine which of the given figures shows a reverse-biased junction diode, we need to analyze the conditions for forward biasing and reverse biasing of a PN junction diode.

### Step-by-Step Solution:

1. **Understanding Forward and Reverse Bias**:
- A PN junction diode is **forward biased** when the P-side (anode) is connected to a higher potential than the N-side (cathode). This allows current to flow through the diode.
- A diode is **reverse biased** when the P-side is connected to a lower potential than the N-side, preventing current from flowing.

2. **Analyzing Each Option**:
- **Option A**:
- P-side voltage = 7V
- N-side voltage = -10V
- Since 7V (P-side) > -10V (N-side), this diode is **forward biased**.

- **Option B**:
- P-side voltage = -10V
- N-side voltage = 0V (earthing)
- Since -10V (P-side) < 0V (N-side), this diode is **reverse biased**.

- **Option C**:
- P-side voltage = 0V (earthing)
- N-side voltage = -10V
- Since 0V (P-side) > -10V (N-side), this diode is **forward biased**.

- **Option D**:
- P-side voltage = -10V
- N-side voltage = 7V
- Since -10V (P-side) < 7V (N-side), this diode is **reverse biased**.

3. **Conclusion**:
- From the analysis, we find that:
- **Option B** and **Option D** are reverse biased.
- Therefore, the correct answer is **B and D**.