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Electrical Properties: Conduction In Metals

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Electrical Properties: Conduction In Metals - Lesson Summary

On the basis of their electrical conductivity values, solids can be classified into three categories - conductors, insulators and semi-conductors.

Conductors have extremely high conductivity values, ranging from 104-107Ohm-1m-1.

Insulators have extremely low conductivities, ranging from 10-20 -10-10 Ohm-1m-1

Semi-conductors have conductivities in the intermediate range - from 10-6 -104 Ohm-1m-1


Conductors:
Depending upon the mode of conduction, conductors can be classified into two types - metallic conductors and electrolytic conductors.


Metallic conductors (or) electronic conductors:
In metallic conductors the conduction is due to the movement of electrons. Metals belong to this category, and conduct electricity without undergoing any change.


Electrolytic conductors:
In electrolytic conductors the flow of electricity is due to the presence of ions. This type of conductors conducts electricity only in their molten and aqueous states.

EX: sodium chloride and potassium chloride are electrolytic conductors.

In metals, the valence band overlaps the conduction band. This results in easy flow of electrons under an applied electric field, and the metal shows conductivity.

Insulators:
In insulators the electrons in the valence band are separated by a large gap from the conduction band. The gap region is called the forbidden zone.

This gap is so large that enough energy is not available under normal conditions to promote electrons from the valence band to the conduction band. Hence, the solid behaves as an insulator.


Semiconductors:
In semi-conductors, the energy gap between the valence band and the conduction band is smaller than in insulators. Thus, only a small amount of current can flow through them.

Semi-conductors can be classified into two categories.


Intrinsicsemi-conductors:
These are composed of only one kind of material.

EX: Silicon and Germanium

These are also called "undoped semi-conductors".


Extrinsicsemi-conductor:
These are made of intrinsic semi-conductors to which other substances have been added to alter their properties.

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