Assertion :When a wire is stretched to two times its length, its resistance becomes 4 times. Reason: Resistance is directly proportional to length of wire.

Both Assertion and Reason are correct and Reason is the correct explanation for Assertion

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Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion

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Assertion is correct but Reason is incorrect

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Assertion is incorrect but Reason is correct

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Solution

The correct option is A Both Assertion and Reason are correct and Reason is the correct explanation for Assertion
Volume of material on stretching remain same. i.e., $A L = V$ constant.
When L becomes 2 times, its area of cross section (A) becomes $1 / 2$ .
From $R = p \frac{L}{A}$ , R would becomes 4 times.

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