SEMICONDUCTOR:
we know that in semiconductor at room temperature the number of charge carriers available are very less.But as temperature increases the number of charge carriers also increases which in turn decreases the resistance.
so the resistance of semiconductor decreases with increase in temperature.
hence semiconductors have negative temperature coefficient.
METAL:
At room temperature metals have more number of charge carriers.generally the temperature has no effect on number of charge carriers.but with increases in temperature the mean free path of electrons decreases.that means as temperature increases the electrons in conduction band will collide each other during their journey(scattering effect).
so resistance will increase with increase in temperature.
hence metals have positive temperature coefficient.
note: In semiconductor the scattering effect is less when compared to the increase of charge carriers with temperature.
In metals the scattering effect is more.
we know that in semiconductor at room temperature the number of charge carriers available are very less.But as temperature increases the number of charge carriers also increases which in turn decreases the resistance.
so the resistance of semiconductor decreases with increase in temperature.
hence semiconductors have negative temperature coefficient.
METAL:
At room temperature metals have more number of charge carriers.generally the temperature has no effect on number of charge carriers.but with increases in temperature the mean free path of electrons decreases.that means as temperature increases the electrons in conduction band will collide each other during their journey(scattering effect).
so resistance will increase with increase in temperature.
hence metals have positive temperature coefficient.
note: In semiconductor the scattering effect is less when compared to the increase of charge carriers with temperature.
In metals the scattering effect is more.
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