Question

a wire of length 1 m,0.02 mm in diameter and has a resistance of 10 ohm . calculate the resistivity of material

Answer 1

Given
length of the wire (l) = 1m
diameter of wire (d) = 0.02 mm = 0.00002m
radius = d/2 = 0.00001 m 
Area of cross section(A) = πr² = 22/7 *0.00001m = 0.00003142 m²
resistance (r) = 10 ohm
Resistivity = RA/l = 10*0.00003142/1 = 0.0003142 ohm m

Answer 2

resistivity=Area* resistance/ length =0.000000314 ohm cm