Determine the strength of the current passing through a steel wire 100 m long and 0.5 mm2, at a voltage of 68V.

Data: l (length of the steel wire taken) = 100 m; S (section of steel wire) = 0.5 mm2; U (effective voltage at the ends of the steel wire) = 68 V.

Constants: ρ (electrical resistivity of steel) = 0.12 Ohm * mm2 / m.

1) Determine the resistance of the steel wire taken: R = ρ * l / S = 0.12 * 100 / 0.5 = 24 Ohm.

2) Calculate the current flowing through the steel wire: I = U / R = 68/24 = 2.83 A.

Answer: A current of 2.83 A flows through the steel wire.