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Choose the only false statement from the following -
A
The resistivity of a semiconductor increases with increase in temperature
B
Substances with energy gap of the order of 10 eV are insulators
C
In conductors the valence and conduction bands may overlap
D
The conductivity of a semiconductor increases with increase in temperature
Detailed Solution
In a semiconductor, as the temperature increases, more electrons gain enough energy to cross the small energy gap into the conduction band, creating more electron-hole pairs.
So the number of charge carriers increases, and the conductivity increases with temperature; that statement is true.
Correspondingly, the resistivity of a semiconductor decreases with increase in temperature (it has a negative temperature coefficient of resistance).
So the statement that the resistivity of a semiconductor increases with temperature is false.
Substances with a large energy gap (more than about 3 eV, for example about 10 eV) are insulators; true.
In conductors (metals) the valence and conduction bands overlap or the conduction band is partly filled; true.
So the only false statement is the one about the resistivity of a semiconductor increasing with temperature.
So the number of charge carriers increases, and the conductivity increases with temperature; that statement is true.
Correspondingly, the resistivity of a semiconductor decreases with increase in temperature (it has a negative temperature coefficient of resistance).
So the statement that the resistivity of a semiconductor increases with temperature is false.
Substances with a large energy gap (more than about 3 eV, for example about 10 eV) are insulators; true.
In conductors (metals) the valence and conduction bands overlap or the conduction band is partly filled; true.
So the only false statement is the one about the resistivity of a semiconductor increasing with temperature.