Answer: Applied electric field.
- A Concentration gradient
- B Applied electric field
- C Temperature gradient
- D Magnetic field only
Correct answer: B. Applied electric field
Explanation: Drift current: carriers move due to electric field. J = sigma × E. Diffusion current: carriers move due to concentration gradient.
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.