The current in a steel conductor 140 cm long and a cross-sectional area of 0.2 mm2 is 250 mA.

The current in a steel conductor 140 cm long and a cross-sectional area of 0.2 mm2 is 250 mA. What is the voltage at the ends of this conductor? Steel resistivity 0.15 Ohm mm2 / m

Data: l (length of steel conductor) = 140 cm = 1.4 m; S (cross-sectional area) = 0.2 mm2; I (current) = 250 mA = 250 * 10-3 A.
Constants: according to the condition ρс (steel resistivity) = 0.15 Ohm * mm2 / m.
To calculate the voltage at the ends of a given steel conductor, we will use the equality: ρ * l / S = R = U / I, whence we express: U = ρ * l * I / S.
Calculation: U = 0.15 * 1.4 * 250 * 10-3 / 0.2 = 0.2625 V ≈ 0.26 V.
Answer: c) the voltage is 0.26 V.