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Alloys such as Nichrome, Manganin and Constantan are preferred for wire-bound standard resistors because
Atheir resistance varies strongly with temperature
Btheir resistivity changes very little with temperature
Cthey have the lowest possible resistivity
Dtheir resistivity drops sharply on heating
Answer & Solution
Correct answer: B. their resistivity changes very little with temperature
1. A standard resistor should keep a fixed value regardless of temperature changes.
2. Nichrome, Manganin and Constantan show only a very weak dependence of resistivity on temperature.
3. Their resistance therefore stays nearly constant during use.
4. So B; a strong dependence (A) or a sharp drop (D) would make them unsuitable.
_Source: NCERT Class 12 Physics Ch 3 "Current Electricity", p.9_
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