Question

A wire with length 15m and diameter 1mm has resistance 0.28Ω. What is the material this wire is made of?

Answer 1

Given:

$l=15\rm\: m$

$d=1\rm\: mm$

$R=0.28\rm\: \Omega$

The resistance of a wire

$$R=\rho\frac{l}{A}=\rho\frac{4l}{\pi d^2}$$

Hence, the resistivity of a material

$$\rho=R\frac{\pi d^2}{4l}\\ =0.28*\frac{3.14*0.001^2}{4*15}=1.5*10^{-8}\:\rm \Omega\cdot m$$

The material is silver.