Classify solids based on their electrical conductivity.

(N/A) Solids are classified into three categories based on their electrical conductivity,which ranges over $27$ orders of magnitude,from $10^{-20}$ to $10^{7} \ ohm^{-1} m^{-1}$.
$(i)$ Conductors: These are solids with conductivities in the range of $10^{4}$ to $10^{7} \ ohm^{-1} m^{-1}$. Metals have conductivities in the order of $10^{7} \ ohm^{-1} m^{-1}$ and are good conductors.
$(ii)$ Insulators: These solids have very low electrical conductivity,ranging from $10^{-20}$ to $10^{-10} \ ohm^{-1} m^{-1}$.
$(iii)$ Semiconductors: These are solids with conductivities in the intermediate range,from $10^{-6}$ to $10^{4} \ ohm^{-1} m^{-1}$.