Three wires of lengths and cross-sectional areas (L, A), (2L, A/2), (L/2,2A) have the same material. In which case is the resistance minimum?
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Three wires of lengths and cross-sectional areas (L,A), (2L,A/2), (L/2,2A) have the same material. In which case is the resistance minimum?

G1 Physics · Accepted Answer

Step 1: R ∝ L/A. Step 2: For (L,A), R₁ = ρL/A; (2L,A/2), R₂ = 4R₁; (L/2,2A), R₃ = R₁/4. Step 3: Minimum resistance corresponds to largest area 2A and shortest length L/2.