Determine the cross-sectional area of a steel wire 100 m long if a current of 2 A flows through it at a voltage of 24 V.

Task data: l (length of the steel wire taken) = 100 m; U (voltage on the wire) = 24 V; I (current) = 2 A.

Reference values: ρ (electrical resistivity of steel at 20 ºС) = 0.15 Ohm * mm2 / m.

To determine the cross section of the steel wire taken, we use the equality: U / I = ρ * l / S = R, whence S = ρ * l * I / U.

Let’s perform the calculation: S = 0.15 * 100 * 2/24 = 1.25 mm2.

Answer: The steel wire taken has a cross section of 1.25 mm2.