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Question
Two wires of same material and same lengths have radii in the ratio of 2 : 3, Compare their resistances.
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Solution
Given: r1 : r2 = 2 : 3
Area of cross-section of wire = a = π r2
∴ a1 : a2 = `"r"_1^2 : "r"_2^2 = 4 : 9`
Resistance of wire R α `1/"a"`
∴ `"R"_1/"R"_2 = "a"_2/"a"_1 = 9/4`
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