WAEC Physics 2015 Objective — Question 40
Question 40 of 50 from the West African Examinations Council (WAEC) Physics 2015 Objective paper, with the correct answer and a full explanation.
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A wire of cross-sectional area 0.60 mm² has a resistivity of 7.2×10⁻⁷ Ωm. Calculate the length of wire that will have a resistance of 3Ω.
- A. 0.25 m
- B. 2.50 mCorrect
- C. 3.60 m
- D. 36.00 m
Explanation
R = ρL/A ⇒ L = RA/ρ = (3×0.6×10⁻⁶)/(7.2×10⁻⁷) = 2.5 m.
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