Answer: In forward bias (electron-hole recombination).
- A In reverse bias, where the depletion region widens
- B Heated externally without any applied bias voltage
- C In forward bias (electron-hole recombination)
- D Cooled well below room temperature with no applied voltage
Correct answer: C. In forward bias (electron-hole recombination)
Explanation: LED: forward bias causes electrons and holes to recombine at junction, emitting photons (light). Color depends on energy gap.
Conductors have overlapping bands, semiconductors have a small energy gap that can be bridged by heat or doping, and insulators have a large gap that blocks conduction.
Concept context
Band theory, p-n junction, diodes, transistors, logic gates, and integrated circuits.