Semiconductors : These are the solids with conductivities in the intermediate range from 10–^6 to 10^4 ohm^–1 m^–1. The forbidden energy gap between the valence band and conduction band is less than 3 eV. Thus energy gap between the valence band and conduction band is small.

Range of Conductor:
A conductor is a material that allows the flow of electric charges easily. In a conductor, the valence electrons are loosely bound, and they are free to move within the material. This mobility of electrons makes a conductor an excellent medium for the conduction of electricity. The range of a conductor can be understood in terms of its conductivity.

- Conductivity: Conductivity is a measure of how easily a material allows the flow of electric charges. It is defined as the reciprocal of resistivity (σ = 1/ρ). Conductivity is measured in siemens per meter (S/m).

- High Conductivity: Conductors have high conductivity, which means they offer very little resistance to the flow of electric charges. This is due to the presence of a large number of free electrons that can move easily in response to an applied electric field. Examples of good conductors include metals like copper (σ = 5.96 x 10^7 S/m), aluminum (σ = 3.50 x 10^7 S/m), and silver (σ = 6.30 x 10^7 S/m).

- Range of Conductor: The range of a conductor is practically infinite. This is because conductors have a very high conductivity, allowing electric charges to flow easily without significant resistance. As long as there is a potential difference (voltage) applied across the conductor, the flow of electric charges will continue.

Range of Insulator:
An insulator is a material that does not allow the flow of electric charges easily. In an insulator, the valence electrons are tightly bound to their respective atoms and cannot move freely. This lack of mobility of electrons makes an insulator a poor conductor of electricity.

- Resistivity: Resistivity is a measure of how strongly a material opposes the flow of electric charges. It is denoted by the symbol ρ and is measured in ohm-meters (Ω.m).

- High Resistivity: Insulators have high resistivity, which means they offer a significant amount of resistance to the flow of electric charges. This is due to the lack of free electrons that can move easily in response to an applied electric field. Examples of insulators include rubber (ρ = 1 x 10^13 Ω.m), glass (ρ = 1 x 10^10 Ω.m), and wood (ρ = 1 x 10^12 Ω.m).

- Range of Insulator: The range of an insulator is also practically infinite. Insulators have very high resistivity, making it extremely difficult for electric charges to flow through them. As long as there is no significant external influence, insulators prevent the flow of electric charges effectively.

Range of Semiconductor:
A semiconductor is a material that has properties between those of a conductor and an insulator. It can conduct electricity under certain conditions but not as easily as a conductor. The range of a semiconductor can be understood in terms of its conductivity and the ability to modify its conductivity.

- Intermediate Conductivity: Semiconductors have intermediate conductivity, which means they offer a moderate amount of resistance to the flow of electric charges. Unlike conductors, the valence electrons in a semiconductor are neither tightly bound nor freely moving. They have a certain energy band structure that allows them to move within the material under specific conditions. Examples of semiconductors include silicon (ρ = 2

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