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The radius $$r$$, length $$l$$ and resistance $$R$$ of a metal wire was measured in the laboratory as $$r = 0.35 \pm 0.05$$ cm, $$R = 100 \pm 10$$ ohm, $$l = 15 \pm 0.2$$ cm. The percentage error in resistivity of the material of the wire is :
ρ = Rl/(πr²). % error = ΔR/R + Δl/l + 2Δr/r = 10/100 + 0.2/15 + 2(0.05/0.35)
= 0.1 + 0.0133 + 0.2857 = 0.399 = 39.9%.
The correct answer is Option 2: 39.9%.
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