Question

an electric power station is connected to a factory by two wires 2.5 km apart of the potential difference between two terminals of the wire at the station is 240 v and at the factory 220 v and the factory uses a current intensity 80 a

Answer 1

$$\Delta V=240-220=20\ V\\R=\frac{20}{80}=0.25\Omega \\\frac{R}{l}=\frac{0.25}{5000}=5.0\cdot 10^{-5}\Omega\cdot m^{-1}$$

$$A=\frac{\rho l}{R}=\frac{1.57\cdot 10^{-8}}{5.0\cdot 10^{-5}}=3.14\cdot 10^{-4}\ m^2$$

$$r=\frac{\sqrt{3.14\cdot 10^{-4}}}{\pi}=0.01\ m$$