The resistance of a copper wire 200 m long is 21 Q. If its thickness (diameter) is 0.44 mm, its specific resistance is around_______________?
Correct answer: C. 1.6 x 10″"8 Q-m
- A. 1.2 x 10~8 Q-m
- B. 1.4 x 10~8 Q-m
- C. 1.6 x 10″"8 Q-m
- D. 1.8 x 10″8 Q-m
Explanation
Using ρ = RA/L and A = πd²/4, the cross-sectional area is about 1.52 × 10⁻⁷ m², giving ρ ≈ 1.6 × 10⁻⁸ Ω·m. This agrees with the known resistivity range of copper.
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