Question

a wire is 0.1m long 0.2meter in diameter and has a resistance of 10 ohm calculate resistivity of its material

Answer 1

We know that R=p*(L/A), 
R=resistance,p=restivity,
A=area of wire=pi*r*r
Given,R=10ohms,
L=0.1mts,
r=(d/2)=0.1mts[d=diameter]
Substituting,we get p(resistivity)=pi ohm-mts.

Answer 2

length of wire = L = 0.1  meters
radius of cross section = r = 0.2 / 2 = 0.1 meters
Area of cross section = π r² = 0.01 π  m²
Resistance R = 10 Ω

Resistivity = ρ

Resistance of the wire = R = ρ L / A
  =>  ρ = A R / L
           = 0.01 π * 10  / 0.1    Ohm-meter
           = π  Ohm-meters