What section is the 8.5 m long copper wire taken so that at a current of 750A

What section is the 8.5 m long copper wire taken so that at a current of 750A the voltage drop across it is 0.3V? Determine the wire diameter.

I = 750 A.

U = 0.3 V.

ρ = 1.7 * 10-8 Ohm * m.

S -?

d -?

We express the resistance of the conductor R according to Ohm’s law for a section of the circuit, the ratio of the voltage at the ends of the conductor U to the current I in the conductor: R = U / I.

Since the conductor is homogeneous and has a cylindrical shape, its resistance R is expressed by the formula: R = ρ * l / S, where ρ is the resistivity of the material from which the conductor is made, l is the length of the conductor, S is the cross-sectional area of ​​the conductor.

U / I = ρ * l / S.

S = ρ * l * I / U.

S = 1.7 * 10-8 Ohm * m * 8.5 m * 750 A / 0.3 B = 0.64 * 10-8 m2.

S = P * d2 / 4.

d = √ (4 * S / P).

d = √ (4 * 0.64 * 10 -8 m2 / 3.14) = 0.9 * 10-4 m.

Answer: the cross-sectional area of ​​the copper wire is S = 0.64 * 10 -8 m2, the wire diameter is d = 0.9 * 10-4 m.