Give two examples of substances which are good conductors of electricity. Why do you think they are good conductors of electricity? b) Calculate the resistance of a copper wire 1.0km long and 0.50mm diameter if the resistivity of copper is 1.7×10-8Ωm.

1. Two examples of substances that are good conductors of electricity are silver and These two metals have free electrons that are available for conduction.
2. Given,

l = 1km = 1000m r = d/2

= 0.5/2mm

= 0.25mm

= 0.25×10-3m

ρ = 1.7×10-8Ωm

We know that, R = ρl/A

R = 86.6Ω