A wire 2.0 m long with cross-sectional area 0.50 mm² has a resistance of 2.2 Ω. What is the resistivity of its material?
Correct answer A. 5.5 × 10⁻⁷ Ω m
Explanation
ρ = RA/L = (2.2 Ω × 0.50 × 10⁻⁶ m²) ÷ 2.0 m = 5.5 × 10⁻⁷ Ω m. Remember 1 mm² = 10⁻⁶ m²; leaving area in mm² gives 0.55 Ω m.
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