Physical Electronics » Notes » Difference between Insulator, Semiconductor and Conductor
Materials can be classified into three groups according to their electrical resistance :
(1) Insulators
(2) Semiconductors
(3) Conductors
Figure 1 – Energy band diagrams for (a) an insulator (b) a semiconductor, and (c) a conductor
Here,
Ev = Top edge of the valence band,
Ec = Bottom edge of the conduction band,
Eg = Bandgap energy or energy gap, Eg = Ec – Ev.
Table 1 – Difference between insulators, semiconductors & Conductors in tabular form
| Charactiristics | Insulator | Semiconductor | Conductor |
| 1. Conductivity | The conductivity of insulator is very low. | The conductivity of semiconductor is moderate. | The conductivity of conductor is very high. |
| 2. Resistivity | It has very high resistivity. | It has moderate resistivity. | It has very low resistivity. |
| 3. Forbidden gap | It has large forbidden gap. | It has small forbidden gap. | It has no forbidden gap. |
| 4. Temperature coefficient of resistance | Insulator has negative temperature coefficient of resistance. | Semiconductor has negative temperature coefficient of resistance | Conductor has positive temperature coefficient of resistance. |
| 5. Electrons availability | There is small number of electrons available for conduction. | There is moderate number of electrons available for conduction. | There is large number of electrons available for conduction. |
| 6. Examples | Paper, Mica glass. | Silicon, Germanium. | Metals, aluminium, copper. |
Table 2 – Comparing of resistivity between insulators, semiconductors & Conductors in tabular form
| S. No. | Substance | Nature | Resistivity |
| 1. | Glass | Insulator | 9 ×1011 Ωm |
| 2. | Germanium | Semiconductor | 0.6 Ωm |
| 3. | Copper | Good conductor | 1.7 ×10−8 Ωm |
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