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If a negligibly small current is passed through a wire of length 15 m and of resistance 5 Ω having uniform cross-section of 6 × 10⁻⁷ m², then coefficient of resistivity of material is

1. 1 × 10⁻⁷ Ω-m
2. 2 × 10⁻⁷ Ω-m
3. 3 × 10⁻⁷ Ω-m
4. 4 × 10⁻⁷ Ω-m

Correct answer: 2 × 10⁻⁷ Ω-m

Solution

The resistivity (ρ) is calculated using the formula ρ = R × A / L, where R is resistance, A is cross-sectional area, and L is length. Substituting the given values: ρ = (5 × 6 × 10⁻⁷) / 15 = 2 × 10⁻⁷ Ω-m.

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