A negligibly small current is passed through a wire of length 15 m and uniform cross-section 6.0 × 10⁻⁷ m² , and its resistance is measured to be 5.0 Ω. What is the resistivity of the material at the temperature of the experiment?

Length of the wire, l =15 m

Area of cross-section of the wire, a = 6.0 x 10⁻⁷ m², Resistance of the material of the wire, R = 5.0Ω. Resistivity of the material of the wire = ρ, Resistance is related with the resistivity as

R = ρ l /A

=> ρ = RA/l

= 5 x 6.0 x 10⁻⁷ / 15 = 2x 10⁻⁷ Ωm

Therefore, the resistivity of the material is 2 x 10^_7Ωm.