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Explain qualitative dependence of resistivity with temperature. |
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Answer» Solution :`rArr` Conductivity of material `sigma= ("ne"^(2) TAU)/(m)` resitivity `rho = (1)/(sigma)` `therefore rho = (m)/("ne"^(2) tau)` If m and e are CONSTANT then, `rho PROP (1)/(n) and rho = (1)/(tau)` Thus, RESISTIVITY is inversely proportional to number density and inversely proportional to relaxation time. ` rArr` With INCREASE in temperature (average ) speed of electron increase hence relaxation time `tau` decrease and resistivity increase. `rArr` IN a metal number density (n ) is not dependent on temperature. `rArr` In semiconductor and insulator number density .n. increase with temperature. Hence, in such material with increase in temperature resistivity decreases. |
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