(i) Define the term drift velocity. (ii) On the basis of electron drift, derive an expression for resistivity of a conductor in terms ofnumber density of free electron and relaxation time. On what factors does resistivity of aconductor depend ?(iii) Why alloys like constantan and manganin are used for making standard resistors ?

(i) Define the term drift velocity. (ii) On the basis of electron drif

1.	(i) Define the term drift velocity. (ii) On the basis of electron drift, derive an expression for resistivity of a conductor in terms ofnumber density of free electron and relaxation time. On what factors does resistivity of aconductor depend ?(iii) Why alloys like constantan and manganin are used for making standard resistors ?
Answer» SOLUTION :(iii) Alloys like CONSTANTAN and manganin are USED for making standard resistors because (a) theirresistivity is comparatively HIGHER, and (b) their temperature coefficient of resistivity is extremelysmall so that the resistance does not CHANGE with change in temperature.

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