The welding machine is connected to the network with copper wires 100 m long and a cross-sectional area of 50 mm2.

The welding machine is connected to the network with copper wires 100 m long and a cross-sectional area of 50 mm2. Determine the voltage on the wires if the current strength in them is 125 A.

l = 100 m.

S = 50 mm2.

I = 125 A.

ρ = 0.017 Ohm * mm2 / m.

U -?

According to Ohm’s law for a section of a circuit, the voltage at its ends U is equal to the product of the current I by its resistance R: U = I * R.

For a homogeneous cylindrical conductor, the resistance R is expressed by the formula: R = ρ * l / S, where S is the cross-sectional area of ​​the conductor, l is the length of the conductor, ρ is the specific resistance of the substance of which the conductor consists.

U = I * ρ * l / S.

According to the table of specific resistance of substances, the specific resistance of copper is ρ = 0.017 Ohm * mm2 / m.

U = 125 A * 0.017 Ohm * mm2 / m * 100 m / 50 mm2 = 4.25 V.

Answer: the voltage across the wires is U = 4.25 V.