What is the resistivity of a 500m long conductor S = 1mm2, if at a voltage of 34V the current is 4 amperes.

l = 500 m.

S = 1mm ^ 2.

U = 34 V.

I = 4 A.

ρ -?

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

We express the resistance of the same conductor R from Ohm’s law for a section of the circuit: R = U / I, where U is the voltage at the ends of the conductor, I is the current strength.

ρ * l / S = U / I.

We find the resistivity of the conductor by the formula: ρ = U * S / I * l.

ρ = 34 V * 1 mm ^ 2/4 A * 500 m = 0.017 Ohm * mm ^ 2 / m.

From the table of the resistivity of substances, we see that this is a copper wire.

Answer: the specific resistance of the conductor is ρ = 0.017 Ohm * mm ^ 2 / m.