Describe the effect of temperature on the electrical resistance of metals and semiconductors.

(N/A) For metals,as temperature increases,the thermal vibrations of the lattice ions increase. This leads to more frequent collisions between free electrons and ions,thereby increasing the resistance. The relationship is given by $R_T = R_0(1 + \alpha \Delta T)$,where $\alpha$ is positive.
For semiconductors,as temperature increases,more charge carriers (electrons and holes) are thermally excited from the valence band to the conduction band. This increase in the number of charge carriers dominates over the effect of increased scattering,leading to a decrease in resistance. Thus,semiconductors have a negative temperature coefficient of resistance.