A wire of length 25 m and cross-sectional area 5 mm² having resistivity of 2 × 10⁻⁶ Ω m is bent into a complete circle. The resistance between diametrically opposite points will be (a) 100 Ω (b) 2.5 Ω (c) 12.5 Ω (d) 50 Ω

Answer: (b). R = (ρ l)/(A) = 2 × 10⁻⁶ × 255 × 10⁻⁶ = 10 Ω Diametrically opposite points: Req = R/4 = 2.5 Ω So the answer is (b) 2.5 Ω.

A wire of length 25 m and cross-sectional area 5 mm² having… | JEE Main 2025 (3 Apr, Shift 1)

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Combination of Resistors

A wire of length 25 m and cross-sectional area $5\text{ mm}^{2}$ having resistivity of $2 \times 10^{-6}\ \Omega\text{ m}$ is bent into a complete circle. The resistance between diametrically opposite points will be

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Answer: (b)

$R = \dfrac{\rho l}{A} = \dfrac{2 \times 10^{-6} \times 25}{5 \times 10^{-6}} = 10\ \Omega$
Diametrically opposite points: $R_{eq} = \dfrac{R}{4} = 2.5\ \Omega$
So the answer is (b) $2.5\ \Omega$ .

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