CBSE 2025, Compartment, Set 1

Question

Assertion (A): The electrical conductivity of a pure Ge crystal increases with increase in its temperature.
Reason (R): The number of electrons excited by thermal excitation from the valence band to the conduction band, in a semiconductor, increases with increase in temperature.

Select the correct option: A). Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of the Assertion (A). B). Both Assertion (A) and Reason (R) are true, but Reason (R) is not the correct explanation of the Assertion (A). C). Assertion (A) is true, but Reason (R) is false. D). Both Assertion (A) and Reason (R) are false.

Edvaya · Accepted Answer

The correct answer is Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of the Assertion (A).. **SOLUTION** **Assertion (A) is True:** The electrical conductivity of an intrinsic (pure) semiconductor like Germanium strictly increases upon heating. **Reason (R) is True:** At higher temperatures, significantly more thermal energy is available to covalently bonded electrons in the valence band, allowing them to jump the energy gap into the conduction band. This massive increase in available charge carriers (electrons and holes) directly accounts for the increased conductivity. Therefore, Reason (R) is the perfect correct explanation for Assertion (A).

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Physics > Modern Physics > Semiconductor Electronics

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