When a potential difference is applied across the current passing through a) an insulator at 0 K is zero b) a semiconductor at 0 K is zero c) a metal at 0 K is finite d) a p-n junction at 300 K is finite, if it is reverse biased

Options

A. A) only a and b are correct
B. B) only c is correct
C. C) only a,b and d are correct
D. D) all are correct

Answer

To solve the question, we need to analyze each statement regarding the behavior of different materials when a potential difference is applied across them at specified temperatures.

**Step 1: Analyze the behavior of an insulator at 0 K.**
- Insulators are materials that do not conduct electricity under normal conditions. At absolute zero (0 K), the thermal energy is minimal, and the electrons are in their lowest energy state, making it impossible for them to move freely. Therefore, when a potential difference is applied across an insulator at 0 K, the current is zero.

**Conclusion for Statement A: True (Current = 0)**

**Step 2: Analyze the behavior of a semiconductor at 0 K.**
- Semiconductors have properties between conductors and insulators. At 0 K, a semiconductor behaves like an insulator because there are no free charge carriers available for conduction. Thus, when a potential difference is applied, the current is also zero.

**Conclusion for Statement B: True (Current = 0)**

**Step 3: Analyze the behavior of a metal at 0 K.**
- Metals conduct electricity due to the presence of free electrons. However, at 0 K, metals become superconductors, which means they have zero resistance. In this state, if a potential difference is applied, the current can be considered infinite, not finite as stated. Therefore, this statement is incorrect.

**Conclusion for Statement C: False (Current = Infinite)**

**Step 4: Analyze the behavior of a p-n junction at 300 K when reverse biased.**
- A p-n junction diode allows current to flow in one direction (forward bias) but blocks it in the reverse bias condition. However, at room temperature (300 K), there is still a small amount of current that flows due to minority carriers even when reverse biased. This current is finite but very small.

**Conclusion for Statement D: True (Current = Finite)**

**Final Conclusion:**
- Statements A, B, and D are correct, while statement C is incorrect. Therefore, the correct answer is that only statements A, B, and D are true.