# What material is a wire with a length of 1 km and a cross section of 10 mm2

What material is a wire with a length of 1 km and a cross section of 10 mm2 made of, if a current of 3 A flows through it, and a voltage of 120 V?

Initial data: l (wire length) = 1 km = 1000 m; S (wire cross-section) = 10 mm2; I (current in the wire) = 3 A; U (voltage on the wire) = 120 V.

1) Determine the value of the resistance of the conductor: R = U / I = 120/3 = 40 Ohm.

2) We calculate the specific resistance of the wire material: R = ρ * l / S, whence ρ = R * S / l = 40 * 10/1000 = 0.4 Ohm * mm2 / m (according to the table of the resistivity of the conductors, the obtained value corresponds to the specific electrical resistance of nickel).

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