Hello, Let detailly know about the conductor,Insulator ,Semiconductor
The electrical conduction properties of different elements and compounds can be explained in
terms of the electrons having energies in the valence and conduction bands. The electrons lying in the lower energy bands, which are normally filled, play no part in the conduction process.
◆Insulators
Stated simply, insulators are those materials in which valence electrons arebound very tightly to their parents atoms, thus requiring very large electric field to remove them from
the attraction of their nuclei. In other words, insulators have no free charge carriers available with them under normal conditions.
In terms of energy bands, it means that insulators (a) have a full valence band,
1. have an empty conduction band,
2. have a large energy gap (of several eV) between them and
3. at ordinary temperatures, the probability of electrons from full valence band gaining sufficientenergy so as to surmount energy gap and thus become available for conduction in the
conduction band, is slight.
For conduction to take place, electrons must be given sufficient
energy to jump from the valence band to the conduction band. Increase in temperature enables some electrons to go to the conduction band which fact accounts forthe negative resistance-temperature coefficient of insulators.
◆Conductors
conducting materials are those in which plenty of free electrons are available for electric conduction. In terms of energy bands, it means that electrical conductors
are those which have overlapping valence and conduction bands
In fact, there is no physical distinction between the two bands.
Hence, the availablity of a large number of conduction electrons.
Another point worth noting is that in the absence of forbidden
energy gap in good conductors, there is no structure to establish
holes. The total current in such conductors is simply a flow of
electrons. It is exactly for this reason that the existence of holes
was not discovered until semi-conductors were studied thoughly
◆Semi Conductors
A semiconductor material is one
whose electrical properties lie in between those of insulators and
good conductors. Examples are : germanium and silicon.
In terms of energy bands, semiconductors can be defined as those materials which have almost
an empty conduction band and almost filled valence band with a very narrow energy gap (of the order of 1 eV) separating the two. At 0ºK, there are no electrons in the conduction band and the valence band is completely filled.
However, with increase in temperature, width of the forbidden energy bands is decreased so thatsome of the electrons are liberated into the conduction band. In other words, conductivity of semiconductors increases with temperature. Moreover, such departing electrons leave behind positive holes in the valence band Hence, semiconductor current is the sum of electron and hole
currents flowing in opposite directions
If u have any doubts feel free to comment below
The electrical conduction properties of different elements and compounds can be explained in
terms of the electrons having energies in the valence and conduction bands. The electrons lying in the lower energy bands, which are normally filled, play no part in the conduction process.
◆Insulators
Stated simply, insulators are those materials in which valence electrons arebound very tightly to their parents atoms, thus requiring very large electric field to remove them from
the attraction of their nuclei. In other words, insulators have no free charge carriers available with them under normal conditions.
In terms of energy bands, it means that insulators (a) have a full valence band,
1. have an empty conduction band,
2. have a large energy gap (of several eV) between them and
3. at ordinary temperatures, the probability of electrons from full valence band gaining sufficientenergy so as to surmount energy gap and thus become available for conduction in the
conduction band, is slight.
For conduction to take place, electrons must be given sufficient
energy to jump from the valence band to the conduction band. Increase in temperature enables some electrons to go to the conduction band which fact accounts forthe negative resistance-temperature coefficient of insulators.
◆Conductors
conducting materials are those in which plenty of free electrons are available for electric conduction. In terms of energy bands, it means that electrical conductors
are those which have overlapping valence and conduction bands
In fact, there is no physical distinction between the two bands.
Hence, the availablity of a large number of conduction electrons.
Another point worth noting is that in the absence of forbidden
energy gap in good conductors, there is no structure to establish
holes. The total current in such conductors is simply a flow of
electrons. It is exactly for this reason that the existence of holes
was not discovered until semi-conductors were studied thoughly
◆Semi Conductors
A semiconductor material is one
whose electrical properties lie in between those of insulators and
good conductors. Examples are : germanium and silicon.
In terms of energy bands, semiconductors can be defined as those materials which have almost
an empty conduction band and almost filled valence band with a very narrow energy gap (of the order of 1 eV) separating the two. At 0ºK, there are no electrons in the conduction band and the valence band is completely filled.
However, with increase in temperature, width of the forbidden energy bands is decreased so thatsome of the electrons are liberated into the conduction band. In other words, conductivity of semiconductors increases with temperature. Moreover, such departing electrons leave behind positive holes in the valence band Hence, semiconductor current is the sum of electron and hole
currents flowing in opposite directions
If u have any doubts feel free to comment below
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