When a wire is stretched double of is length, then its resistance will be
Correct answer: B. 4 R
- A. 16 R
- B. 4 R
- C. 2 R
- D. 8 R
Explanation
When a wire is stretched to double its original length, the cross-sectional area is reduced to maintain constant volume. Since resistance (R) is proportional to length (L) and inversely proportional to cross-sectional area (A), the resistance of the wire when stretched becomes R' = ρ(L'/A'). If the length is doubled, the cross-sectional area is halved, leading to the new resistance being R' = ρ(2L)/(A/2) = 4R. Therefore, option B is correct. Options A, C, and D are incorrect because they do not accurately account for the square relationship between the change in length and the resulting change in resistance.
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