A wire of length 25 m and cross-sectional area 5 mm² has resistivity 2×10⁻⁶ Ω m. It is bent into a complete circle. The resistance between diametrically opposite points is:
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Question

A wire of length 25 m and cross-sectional area 5 mm² has resistivity 2×10⁻⁶ Ω m. It is bent into a complete circle. The resistance between diametrically opposite points is:

G1 Physics · Accepted Answer

Resistance of the complete wire is R = ρL/A. Convert area: A = 5 mm² = 5×10⁻⁶ m². Therefore, R = (2×10⁻⁶)(25)/(5×10⁻⁶) = 10 Ω. Between diametrically opposite points, the circular wire divides into two equal semicircular paths. Each has resistance R/2 = 5 Ω. These two 5 Ω resistances are in parallel: R e q R_eq R e ​ q = (5×5)/(5+5) = 25/10 = 2.5 Ω. Correct answer: 2.5 Ω. Note: the source paper's printed options contain a typo and do not list 2.5 Ω; this Excel version corrects option A so that t…