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Given below are two statements: One is labelled as Assertion A and the other is labelled as Reason R. Assertion A: Alloys such as constantan and manganin are used in making standard resistance coils. Reason R: Constantan and manganin have very small value of temperature coefficient of resistance. In the light of the above statements, choose the correct answer from the options given below.

Asked in JEE Main 29th July 2nd Shift 2022 · Temperature dependence of resistance

• (1) Both A and R are true and R is the correct explanation of A.
• (2) Both A and R are true but R is NOT the correct explanation of A.
• (3) A is true but R is false.
• (4) A is false but R is true.

Step-by-step solution

Why the other options are wrong

• (2) R is exactly why these alloys are chosen: a tiny α keeps the coil's resistance steady as it warms.
• (3) R is true: manganin and constantan have a very small temperature coefficient.
• (4) A is true: standard resistors are indeed wound from manganin and constantan.

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