2 CLASSIFICATION OF METALS, CONDUCTORS AND
SEMICONDUCTORS
On the basis of conductivity
On the basis of the relative values of electrical conductivity (s ) or resistivity
(r = 1/s ), the solids are broadly classified as:
(i) Metals: They possess very low resistivity (or high conductivity) r ~ 10–2 – 10–8 W m
s ~ 102 – 108 S m–1
(ii) Semiconductors: They have resistivity or conductivity intermediate
to metals and insulators r ~ 10–5 – 106 W m
s ~ 105 – 10–6 S m–1
(iii)Insulators: They have high resistivity (or low conductivity) r ~ 1011 – 1019 W m
s ~ 10–11 – 10–19 S m–1
The values of r and s given above are indicative of magnitude and
could well go outside the ranges as well