250+ TOP MCQs on Semiconductor Electronics – Special Purpose p-n Junction Diodes | Class12 Physics

Physics Multiple Choice Questions on “Semiconductor Electronics – Special Purpose p-n Junction Diodes”.

1. Which of the following is operated in forward bias?
a) LED
b) Zener diode
c) Photodiode
d) Solar cell
Answer: a
Clarification: A light-emitting diode (LED) converts electric energy into light energy. A LED is a heavily doped p-n junction which under forward bias emits spontaneous radiation. The semiconductor used for the fabrication of visible LEDs must at least have a bandgap of 1.8 eV.

2. Which of the following converts light energy to electric current?
a) LED
b) Zener diode
c) Photodiode
d) Solar cell
Answer: c
Clarification: A photodiode is a semiconductor device, which converts light energy to electric energy. It is a special type p-n junction diode fabricated with a transparent window to allow light to fall on the diode. Photodiodes are operated in reverse bias.

3. Identify the one on which no external bias is applied.
a) Zener diode
b) Solar cell
c) Photodiode
d) Light-emitting diode
Answer: b
Clarification: Solar cells convert solar energy into electric energy. A solar cell is a p-n junction that generates emf when solar radiation falls on the p-n junction. It works on the same principle as the photodiode, except that no external bias is applied and the junction area is kept large.

4. The I-V characteristics of a LED are similar to that of Si junction diode.
a) True
b) False
Answer: a
Clarification: Yes, this is a true statement. The I-V characteristics of a LED are indeed similar to that of Si junction diode. But the threshold voltages are much higher and slightly different for each color. The reverse breakdown voltages of LEDs are very low, typically around 5 V.

5. Which of the following is used as a voltage regulator?
a) Photodiode
b) Solar cell
c) LED
d) Zener diode
Answer: b
Clarification: Zener diode was invented by Clarence Melvin Zener. It is designed to operate under reverse bias in the breakdown region and is used as a voltage regulator. It is designed to allow current to flow backward.