The conductivity of a semiconductor incr...

The conductivity of a semiconductor increases with increase in temperature because

(a) number density of free current carries increases

(b) relaxation time increases

both number density of carriers and relaxation time decreases but effect of decrease in relaxation time is much less than increase in number density .

(d) number density of current carriers increases, relaxation time decreases but effect of decrease in relaxation time is much less than increases in number density

Text Solution

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The correct Answer is:

With increase in temperature , number of electrons reaching conduction band increases but , mean relation time decreases . Effect of decrease in relation time is much less than that of increase in number density of charge carriers.

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Assertion (A) : The electrical conductivity of a semiconductor increases with increase in temperature. Reason (R ) : With increase in temperature, large number of electrons from the valence band can jump to the conduction band.

If both `(A)` and `(R)` are correct, and `(R)` is the correct explanation of `(A)`

If both `(A)` and `(R)` are correct, but `(R)` is not the correct explanation of `(A)`

If `(A)` is correct, but `(R)` is incorrect.

If both `(A)` is incorrect, but `(R)` is correct.

Statement 1: Conductivity of semiconductor increases with increase in temperature. Statement 2: Forbidden energy gap is highest for semiconductors.

Both Statement-1 and Statement-2 are true, and Statement-2 is the correct explanation of Statement-1.

Both Statement-1 and Statement-2 are true but Statement-2 is not the correct explanation of Statement -1.

Statement-1 is true but Statement-2 is false.

Statement-1 is false but Statement-2 is true.

Statement 1: Conductivity of semiconductors decreases with increase in temperature Statement-2: More electron goes from valance band to conduction band with increase in temperature.