Historical Classification due to conductivity:

Historical Classification due to conductivity:
Nonconductor (Insulator):
Very few free electrons, or no free electrons at all, which
contribute to electrical current. Hence, very low conductivity,
or no conductivity at all.
Dr. Thomas F. BECHTELER Izmir University Electronics and Communication Engineering Dept.
Semiconductor:
A few free electrons which contribute to electrical current.
Hence, conductivity, which is between the conductivity of
conductors and that of insulators.
Conductor:
Huge amount of free electrons which contribute to electrical
current. Hence, conductivity is very high.
Superconductor (see more in “Modern Physics”):
New state of the material below a so-called critical temperature
Tc. Two electrons form a new particle called Cooper-Pair
which does not interact with the atom bodies. Hence, no
losses and therefore zero resistance!