WAEC Physics 2016 Objective — Question 34
Question 34 of 50 from the West African Examinations Council (WAEC) Physics 2016 Objective paper, with the correct answer and a full explanation.
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34. An aluminium cable of diameter 4×10⁻³ m and resistivity 3.0×10⁻⁸ Ωm has a resistance of 21Ω. Calculate the length of the cable. (π=3.14) A. 8.0×10² m B. 8.8×10³ m C. 8.0×10⁴ m D. 8.8×10⁴ m
- A. 8.0×10² m
- B. 8.8×10³ m
- C. 8.0×10⁴ m
- D. 8.8×10⁴ mCorrect
Explanation
R=ρL/A, A=πd²/4; L=RA/ρ = 21×π×(4×10⁻³)²/(4×3×10⁻⁸) = 8.8×10⁴ m.
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