Question

A 3.7-mm-diameter wire carries a 20 A current when the electric field is 8.2×10−2 V/m .

Answer 1

Answer:

   ρ = 4.4 10⁻⁸ Ω m

Explanation:

For this exercise let's start by finding the value of the resistance using Ohm's law

          V = I R

           R = V / I

   

The voltage is related to the electric field

          V = E L

           

let's substitute

          R = E L / I

          R = 8.2 10⁻² / 20  

          R = 4.1 10⁻³ L

now we can use the resistance relation

          R = ρ L / A

the area of ​​a circular wire is

          A = π r² = π d² / 4

         ρ = R π d² / (4 L)

let's calculate

        ρ = (4.1 10⁻³ L) π 0.0037² / (4 L) = (4.1 10⁻³) π 0.0037² / (4)

        ρ = 4.4 10⁻⁸ Ω m