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Question
Two wires of the same material and same length have radii 1 mm and 2 mm respectively. Compare their resistances.
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Solution
`"R"_1 ∝ 1/(pir_1^2)`
`"R"_2 ∝ 1/(pir_2^2)`
∴ `"R"_1/"R"_2 = (pir_2^2)/(pir_1^2)`
∴ `"R"_1 : "R"_2 = r_2^2 : r_1^2`
= 22 : 12
= 4 : 1
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