question_answer

Directions : (11-15)

Temperature Dependence of Resistivity

The resistance of a conductor at temperature \[t{}^\circ C\] is given by \[{{R}_{t}}={{R}_{0}}\left( 1+\alpha t \right)\]

Where \[{{R}_{t}}\] is the resistance at \[t{}^\circ C\], \[{{R}_{0}}\] is the resistance at \[0{}^\circ C\] and \[\alpha \] is the characteristics constants of the material of the conductor.

Over a limited of range of temperatures, that is not too large. The resistivity of a metallic conductor is approximately given by \[{{\rho }_{t}}={{\rho }_{0}}\left( 1+\alpha t \right)\].

Where \[\alpha \] is the temperature coefficient of resistivity. Its unit is \[{{K}^{-1}}\]or \[{}^\circ {{C}^{-1}}\].

For metals \[\alpha \] is positive i.e., resistance increases with rise in temperature.

For insulators and semiconductors, \[\alpha \] is negative i.e., resistance decreases with rise in temperature.

Fractional increase in resistivity per unit increse in temperature is defined as :

A) resistivity

B) temperature coefficient of resistivity

C) conductivity

D) drift velocity