Write a note on the classification of materials based on their conductivity.

(A) Materials are classified into conductors,insulators,and semiconductors based on the magnitude of their electrical conductivity.
$1$. Conductors: These materials have very high conductivity. Examples include metals and their alloys (e.g.,$Na, Cu, Ag, Au, Fe$),certain non-metals like carbon black and graphite,and some electronically conducting organic polymers.
$2$. Insulators: These materials have very low conductivity. Examples include glass,ceramics,and polymers like Teflon.
$3$. Semiconductors: These materials have conductivity values between those of conductors and insulators. Examples include silicon,doped silicon,gallium arsenide,and certain oxides like $CuO$. These are important electronic materials.
$4$. Superconductors: These are materials that exhibit zero resistivity or infinite conductivity. While earlier only metals and alloys at very low temperatures ($0 \ K$ to $15 \ K$) were known to be superconductors,many ceramic materials and mixed oxides are now known to exhibit superconductivity at temperatures as high as $150 \ K$.