Electrical Properties Of Solid

The above note is all about the electrical properties of solid.The solids can be grouped into four categories on the basis of electrical conductivity.They are conductor,insulator,semiconductor and superconductor.A solid which allow the passage of electric current are called conductors.The solids which do not allow the passage of electric current through them are called insulators.Metals are good conductors of heat and electricity and their electrical conductivity decreases with the increase in temperature..Those substances which have zero or almost zero electrical resistance and carry an electrical current without losing energy are called superconductors.The solid whose conductivity lie between those of mettalic conductor and insulator are called semiconductors.

Summary

Things to Remember

What is a Solid State?

Matter exists in three physical states - Solid, Liquid and Gas. The existence of any state depends upon two main forces,

Intermolecular forces : The force which binds the constituent particles and tries to keep them close together.
Thermal energy : This is the energy which tries to keep the particles apart and makes their movement fast.

At low temperature, the thermal energy is low and intermolecular forces are strong, so the particles occupy fixed positions and can oscillate about their mean position. The compound exists in solid state.

A solid is defined as that form of matter which possesses rigidity and hence possesses a definite shape and a definite volume.

General Characteristic of Solids

As mentioned above, a solid has two main properties:
They have strong intermolecular forces and short inter nuclear distance due to close packing of constituent particles. Their constituent particles don’t possess translator motion but can oscillate only about their mean position.

Due to these two basic properties, the solid possesses the following characteristic properties.

They have a particular shape, mass and volume
They are rigid and incompressible
They have high density

Classification of Matter

Matter can exist in three physical states which are solid, liquid and gas.

Solid	Liquid	Gases
They have definite shape and volume.	They have definite volume but no definite shape.	Neither have definite shape nor volume.
Have many surfaces.	Have one surface.	No surface.
Have a melting point above room temperature.	Have melting point below room temperature.	The boiling point is much below room temperature.
For example-sugar iron, wood etc	For example-oil, mercury, water etc.	For example-Hydrogen, oxygen, air etc.

The three states are inter convertible by changing the conditions of temperature and pressure as shown below-

Solids show a wide range of electrical conductivities from 10^-20 to 10⁷ ohm^-1 m^-1. On the basis of electrical conductivity the solid can be broadly classified into three types:

Metals (conductors)

The solids which have conductivities in order of 10⁴ to 10⁷ ohm^-1 m^-1. Metals are good conductors of electricity.

Insulators

Solids which have very low conductivity in the range 10^-20 to 10^-10ohm^-1 m^-1. For example wood, rubber, sulfur, phosphorus etc.

Semiconductors

Their conductivity is in between conductor and insulator up to the order of 10^-6 to 10⁴ ohm^-1 m^-1.

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Electrical Properties Of Solid

Electrical Conductivity

Solid exhibit an interesting range of variation of electrical conductivities extending over 27 orders of magnnitude in which no other physical properties shows Electrical properties of solids are measured in terms of conductivity. Conductivity may be defined as the ease with which electric current can pass through a given substance. All solids do not conduct electricity in equal amounts. Some of them have high conductivity, whereas some of them do not conduct electricity at all..On the basis of electrical conductivity,solids can be classified into following types.

i)Conductor

ii)Semiconductor

iii)Insulator

iv)Superconductor

The conductivity of solid id one of the characteristic properties.Electrical conductivity of metal is very high and in the order of 10^-7ohm^-1.On the other hand,insulators have a conductivity in the range of 10^-10to 10^-20 ohm^-1.But semiconductors have a intermediate range of conductivity.

Conductor

A solid which allow the passage of electric current are called conductors. Metals are generally good conductors of electricity. Electrical conductivity in metals is due to the presence of mobile electrons. The conductivity of metals is of the order of 10⁷(Ωm)^-1. There is no gap between the conduction band and the valence band. Thus electrons can easily flow from the valence band to the conduction band under the influence of electric field, making them good conductors of electricity..There are two types of conductors.They are:

a)Metallic conductors

b)Electrolytic conductors

Metallic conductor

Those conductor which conduct electricity due to the migration of mobile free electrons without undergoing any chemical changecare called metallic conductors.Conductivity of metallic conductor decreases with the increase in temperature.

Electrolyic Conductivity

Those conductor which conduct electricity through them by undergoing a chemical change are called electrolytic conductors.The conductivity of electrolytic conductor is due to the migration of ions or charged particles.

ii)Semiconductor

The solid whose conductivity lie between those of mettalic conductor and insulator are called semiconductors.Typical metals are good conductors of electricity while elements like silicon and germanium are non-conductors at ordinary temperature.However they exhibit appreciable conductivity due to the addition of impurities like arsenic and boron.The resulting materials are semiconductors.There are two types of semi conductors.

a)n-type semiconductor

Semi conductors which are obtained by adding impurities like arsenic,antimony,phosphorus,etc having 5 valence electrons to the pure silicon are called n-type semiconductors.

b)p-type semiconductor

Semiconductors which are obtained by adding impurities by adding impurities like boron,aluminium,gallium, having 3 valence electrons to the pure silicon are called p-type semiconductor.

iii)Insulator

The solids which do not allow the passage of electric current through them are called insulators.The band gap between the valence band and conduction band is very large. Even if a large amount of energy is provided to these solids, they do not conduct electricity.Example: Wood,plastics etc.

iv)Superconductor

Metals are good conductors of heat and electricity and their electrical conductivity decreases with the increase in temperature.It means conductivity increases with the decrease in temperature.Those substances which have zero or almost zero electrical resistance and carry an electrical current without losing energy are called superconductors.Metals such as mercury,lead become superconductor at absolute zero.

References

Prutton, S.H Maron & c. Principles of Physical Chemistry. Oxford & Pub. Co., 1992.

Lesson

Solid State Chemistry

Subject

Chemistry

Grade

Bachelor of Science

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