What is the resistivity of a tram wire if its length is 10 km, cross-sectional area is 70 mm2, resistance is 3.5 Ohm.

Task data: l (tram wire length) = 10 km; S (cross-sectional area) = 70 mm2; R (tram wire resistance) = 3.5 ohms.

SI system: l = 10 km = 10 * 103 m.

We calculate the electrical resistivity of the material from which the tram wire is made from the formula: R = ρ * l / S and ρ = R * S / l.

Let’s make a calculation: ρ = R * S / l = 3.5 * 70 / (10 * 103) = 0.0245 Ohm * mm2 / m.

Answer: The specific electrical resistance of the tram wire material is 0.0245 Ohm * mm2 / m.