The resistance of a metal wire of length 3 m is 60Ω. If the area of cross-section of the wire is 4×1

(i) Write the relation between resistance R and electrical resistivity ρ of the material of a conductor in the shape of cylinder of length I and area of cross-section A. Hence derive the SI unit of electrical resistivity. (5 M) (2024) (ii) The resistance of a metal wire of length 3 m is 60Ω. If the area of cross-section of the wire is 4×10 −7m , calculate the electrical resistivity of the wire. (iii) State how would electrical resistivity be affected if the wire (of part ' ii ′) is stretched so that its length is doubled. Justify your answer.