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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. (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.

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.

Correct answer: A is false but R is true.

Solution

Assertion A is incorrect because while constantan and manganin are indeed used in standard resistance coils, they are not the only materials used for this purpose. However, Reason R is correct as both alloys have low temperature coefficients of resistance, which is a desirable property for maintaining stable resistance values.

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