oblicz opor miedzianego drutu o dlugosci 2km i średnicy 1mm  

[latex]d=1mm[/latex] więc [latex]r=0,5mm[/latex] [latex]l=2km=2000m[/latex] [latex] ho=0,0182frac{Omegacdot mm^2}{m}[/latex] [latex]S=picdot r^2=picdot 0,25=0,785mm^2[/latex] [latex]R= hofrac{l}{s}=0,0182frac{2000}{0,785}=46,37Omega[/latex]