Question

a copper wire of length 2 m and area of cross section 1.7 X 10-6 m has a resistance of 2 X 10-2 ? Calculate resistivity of copper ?

Answer 1

Length of the copper wire l = 200 m
        Diameter of the copper wire = d = 1 mm = 1 x 10−3 m
        Radius of the copper wire r = d/2 = 5 x  10−4 m
        Area of cross section of the copper wire A = π r2 = 3.14 x (5 x  10−4 m)2
                                                                                                       = 78.5 x 10−8 m2
       Resistivity of copper ρ = 1.7 x 10-8 Ωm
       Resistance of the copper wire R = ρl/A = 1.7 x 10-8 Ωm x 200 m/(78.5 x 10−8 m2)
                                                                                    = 4.33 Ω