Pn Junction

Step 1: Understanding Ohm's law.
Ohm's law states that the current through a conductor is directly proportional to the voltage across it, and inversely proportional to the resistance. For a material to obey Ohm's law, its resistance must remain constant as the current and voltage vary.
Step 2: Behavior of semiconductors.
Semiconductors do not always obey Ohm’s law. The resistance of semiconductors depends on the temperature and the applied voltage. When a semiconductor is doped (either n-type or p-type), its resistance can change, making its behavior non-linear. As a result, semiconductors have a current-voltage relationship that does not follow Ohm's law.
Step 3: Conclusion.
Thus, a semiconductor does not obey Ohm's law in all cases, making the statement false.

Step 1: Understanding p-n junction and biasing.
In a p-n junction, when a forward bias is applied (positive terminal connected to the p-type and negative terminal to the n-type), the potential barrier at the junction decreases. This allows charge carriers (electrons and holes) to move across the junction, leading to current flow.
Step 2: Effect of forward bias.
Forward bias reduces the width of the depletion region, thereby reducing the potential barrier. This enables easier flow of current through the junction.
Step 3: Conclusion.
Thus, applying forward bias in a p-n junction causes the potential barrier to decrease, corresponding to option (A).

Step 1: V-I Characteristics of a p-n junction.
In a p-n junction diode, when reverse bias is applied, the current is very small until the reverse voltage reaches a certain point, called the breakdown voltage.
Step 2: Understanding reverse bias.
In reverse bias, the positive terminal of the battery is connected to the n-type material and the negative terminal to the p-type material. This causes the depletion region to widen, and the current remains very small (called the reverse leakage current).
Step 3: Breakdown voltage.
If the reverse bias is increased beyond a certain point (breakdown voltage), the diode experiences a sharp increase in current due to avalanche breakdown or Zener breakdown. The V-I characteristic shows a steep rise in current after reaching the breakdown voltage.
Step 4: Circuit diagram.
The circuit diagram for reverse biasing of a p-n junction diode is: The V-I characteristic curve would show a very small current initially and then a sharp increase once the breakdown voltage is reached.
Step 5: Conclusion.
In reverse bias, the current through a p-n junction diode remains very small until the breakdown voltage is reached, beyond which the current increases sharply.

Step 1: Reverse Biasing of a p-n Junction Diode.
In reverse bias, the positive terminal of the battery is connected to the n-type material of the diode, and the negative terminal is connected to the p-type material. This causes the depletion region to widen, and the current becomes very small (called reverse leakage current).
Step 2: V-I Characteristics.
The current in a p-n junction diode under reverse bias remains very small up to a certain voltage. When the reverse voltage reaches the breakdown voltage, the current increases drastically due to processes like avalanche breakdown or Zener breakdown.
Step 3: Diagram of the circuit.
In the diagram, the p-n junction diode is placed in a reverse-biased circuit. Initially, no current flows, but once the voltage exceeds the breakdown voltage, a large current flows.
Step 4: Conclusion.
In reverse bias, the current remains very small until the breakdown voltage is reached. After that, the current increases rapidly.