| Assertion (A): As the temperature of a semiconductor increases, its resistance decreases. |
| Reason (R): The energy gap between conduction band and valence band is small. |
A) Both A and R are true and R is the correct explanation of A
B) Both A and R are true but R is NOT the correct explanation of A
C) A is true but R is false
D) A is false and R is true
Correct Answer: A
Solution :
| Option [a] is correct. |
| Explanation: As temperature rises, the electrons of valence band sufficient energy and jump to conduction band. Thus, the resistivity decreases. So assertion is true. |
| In semiconductors the energy gap between conduction band and valence band is small. |
| Due to this, the electrons in conduction band can gain sufficient thermal energy with temperature rise and can easily jump across the small energy gap to reach conduction band. |
| Thus, conductivity increases and resistance decreases. |
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