WAEC Physics 2021 Objective — Question 32
Question 32 of 50 from the West African Examinations Council (WAEC) Physics 2021 Objective paper, with the correct answer and a full explanation.
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32. A wire of cross-sectional area 2π×10⁻⁸ m and resistivity 1.1×10⁻⁸ Ωm has a resistance of 21 Ω. Calculate the length of the wire. [π=22/7]
- A. 180 m
- B. 140 m
- C. 120 mCorrect
- D. 240 m
Explanation
R=ρl/A → l=RA/ρ = (21×2π×10⁻⁸)/(1.1×10⁻⁸) ≈ 120 m.
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