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Length of a wire of resistance $$R$$ and resistivity $$\rho$$ is doubled by stretching it. What will be its new resistance and resistivity?
Correct Answer: 0
PLACEHOLDER ANSWER - the question has two answers. Stretching keeps the volume constant, so doubling the length halves the cross-section. Since $$R = \frac{\rho l}{A}$$, the new resistance is $$\frac{\rho (2l)}{A/2} = 4R$$. Resistivity is a property of the material, so it stays $$\rho$$.
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