Question: Q. 2. (i) Define the term drift velocity.
(ii) On the basis of electron drift, derive an expression for resistivity of a conductor in terms of number density of free electrons and relaxation time. On what factors do resistivity of a conductor depend ?
R [Delhi I, II, III 2016]
(iii) Why alloys like constantan and manganin are used for makingstandard resistors?
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Solution:
Ans. (i) Try yourself Similar to Q. 11 (i), Short Answer
Type Question-II
$1 \frac{1}{2}$
(ii) Try yourself Similar to Q. 2 (ii), short Answer Type Question-II
Resistivity of the material of a conductor depends on the relaxation time, i.e., temperature and the number density of electrons.
(iii) Constantan and Manganin are used to make standard resistors because
(a) they have high value of resistivity
(b) temperature coefficient of resistance is less
(c) they are least affected by temperature
(d) show weak dependence of resistivity on temperature
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[CBSE Marking Scheme 2016]
