Question

Write the relation between resistance R and electrical resistivity ρ of the material of a conductor in the shape of cylinder of length l and area of cross-section A. Hence derive the SI unit of electrical resistivity.

The resistance of a metal wire of length 3 m is 60 Ω. If the area of cross-section of the wire is 4×10⁻⁷ m², calculate the electrical resistivity of the wire.

State how would electrical resistivity be affected if the wire (of part 'ii') is stretched so that its length is doubled. Justify your answer.

The resistance of a wire of 0·01 cm radius is 14 Ω. If the resistivity of the material of the wire is 44 × 10⁻⁸ Ωm, find the length of the wire. (Given π = 22/7)