A copper wire is drawn so that its length increases by 0.5%, while its volume stays the same. By what percentage does its electrical resistance change?

2.5%
0.5%
1.0%
2.0%

Correct answer: 1.0%

Solution

With volume fixed, resistance varies as the square of length, so the percentage change in R is twice the percentage change in L: 2 * 0.5% = 1.0%.

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