What is conductor insulator and semiconductor

1. Insulator

Through these materials electricity cannot pass is called insulators. Plastic, glass, wood, etc are examples of insulators. The valence band of those material remains full of electrons. The conduction band of those material remains empty. The forbidden energy gap between the conduction band and the valence band is widest. The difference is more than 10ev. Crossing the forbidden energy gap from the valence band to the conduction band a large amount of energy is needed.
2. Conductor

An electrical conductor is a substance in which electrical charge carriers, usually electron

move easily from atom to atom with the application of voltage. Conductivity, in general, is the capacity to transmit something, such as electricity or heat.

Pure elemental silver is the best electrical conductor encountered in everyday life. Copper, steel, gold, aluminum, and brass are also good conductors. In electrical and electronic systems, all conductors comprise solid metals molded into wires or etched onto circuit boards.

Some liquids are good electrical conductors. Mercury is an excellent example. A saturated salt-water solution acts as a fair conductor. Gases are normally poor conductors because the atoms are too far apart to allow a free exchange of electrons. However, if a sample of gas contains a significant number of ions, it can act as a fair conductor.

3. Semiconductor

A semiconductor is a substance, usually a solid chemical element or compound, that can conduct electricity under some conditions but not others, making it a good medium for the control of electrical current. Its conductance varies depending on the current or voltage applied to a control electrode, or on the intensity of irradiation by infrared (IR), visible light, ultraviolet (UV), or X rays.

The specific properties of a semiconductor depend on the impurities, or doping added to it. An N-type semiconductor carries current mainly in the form of negatively-charged electrons, in a manner similar to the conduction of current in a wire. A P-type semiconductor carries current predominantly as electron deficiencies called holes. A hole has a positive electric charge, equal and opposite to the charge on an electron. In a semiconductor material, the flow of holes occurs in a direction opposite to the flow of electrons.

A semiconductor device can perform the function of a vacuum tube having hundreds of times its volume. A single integrated circuit (IC), such as a microprocessor chip, can do the work of a set of vacuum tubes that would fill a large building and require its own electric generating plant.