COMEDK20269 May 2026Evening ShiftPhysicsSemiconductorsActual
Pick out the correct statement from the following;
Options
- AValance band is always completely filled, while conduction band is always partially filled
- BThe number density of free electrons in the valance band decides the strength of the electric current
- CThe maximum energy required to shift an electron from the conduction band to valance band is called energy ban
- DIn a semiconductor no free electrons are found in the conduction band at 0 K
Correct answer
D. In a semiconductor no free electrons are found in the conduction band at 0 K
Step-by-step solution
At 0 K , all the electrons in a semiconductor are tightly bound to their respective atoms. The valence band is completely filled and the conduction band is completely empty. Since there are no free electrons in the conduction band at 0 K , a semiconductor behaves as a perfect insulator. The energy band gap is the minimum energy required to shift an electron from the valence band to the conduction band, making option C incorrect. Electric current is determined by the number density of free electrons in the conductio