Question

A 20 metre length of cable has a cross-sectional area of 1mm2and a resistance of 5 ohms.  Calculate the conductivity of the cable. 

Answer 1

Gives

l=20m

Area(A)=1mm²

R=5ohm

We know that

$R=\frac{\rho l}{A}$

$\rho=\frac{RA}{l}$

Put value

$$\rho=\frac{5\times10^{-6}}{20}=2.5\times10^{-7}\Omega m$$

We know that

$\sigma=\frac{1}{\rho}$

$$\sigma=\frac{1}{2.5\times10^{-7}}=4\times10^6mho/m$$