Assertion (A): The temperature coefficient of resistance is positive for p-type semiconductors and negative for n-type semiconductors.
Reason (R): The effective charge carriers in p-type semiconductors are electrons and in n-type semiconductors are holes.
1. Both (A) & (R) are true and the (R) is the correct explanation of the (A)
2. Both (A) & (R) are true but the (R) is not the correct explanation of the (A)
3. (A) is true but (R) is false
4. Both (A) and (R) are false
View Answer
All semiconductors (p-type or n-type) have a negative temperature coefficient of resistance, so (A) is false. In p-type semiconductors, majority carriers are holes, and in n-type, they are electrons. Reason (R) swaps these, so it is also false. Thus, both (A) and (R) are false.
Assertion (A): The probability of electrons to be found in the conduction band of an intrinsic semiconductor at a finite temperature decreases exponentially with increasing band gap.
Reason (R): It is more difficult for the electrons to jump to the conduction band from the valence band if the band gap between them is large.
1. Both (A) & (R) are true and the (R) is the correct explanation of the (A)
2. Both (A) & (R) are true but the (R) is not the correct explanation of the (A)
3. (A) is true but (R) is false
4. Both (A) and (R) are false
View Answer
Assertion (A) is true: The probability of finding electrons in the conduction band is proportional to \(e^{-E_g / (2kT)}\), decreasing exponentially with band gap \(E_g\).
Reason (R) is true: A larger band gap means more energy is required for electrons to jump. Reason (R) correctly explains Assertion (A).