question_answer

The temperature (T) dependence of resistivity (\[\rho \]) of a semiconductor is represented by :

A)

B)

C)                

D)                

Correct Answer: B

Solution :

                The variation of specific resistance with temperature is as follows \[\rho ={{\rho }_{ref}}+[1+\alpha (T-{{T}_{ref}})]\] where \[\rho \]= specific resistance at temperature T \[{{\rho }_{ref}}\] = specific    resistance    of   reference temperature \[\alpha \] = temperature of coefficient of resistance. Rearranging the terms we have \[\rho ={{\rho }_{0}}+{{\rho }_{0}}\,\,\alpha \,(T-{{T}_{0}})\] On comparing the equation with equation of straight line \[y=mx+c\] we have, the slope negative. Note: The temperature coefficient of resistance of semiconductors is negative that is their electrical resistance decreases (or conductivity increases) with rise in temperature. At absolute zero a semiconductor behaves as an ideal insulator.