Conductors, Insulators and Semi-conductors
Electric current moves easily through some materials but with greater difficulty through others. Let us see how the action of free electrons is related to current flow through these materials.
Conductors:
Some substances let electric charge flow through them. These substances are called conductors. Conductors permit the movement of a large number of free electrons. One of the best-known conductors is copper. It conducts so well because the electrons of copper atoms are able to escape easily from the atoms. The best conductors are metals. Copper is the most commonly used conductor because it conducts electric charge better than any metal, except silver. But silver is too expensive to be used. Copper wires are used in almost all electronic equipment. The tracks on a circuit board are also made of copper.
Insulators:
These substances contain few or no free electrons, so they are not able to conduct electric charge. We sometimes call them non-conductors. Insulators included substances such as: Many types of plastic, including polyvinyl chloride (PVC), which is used for insulating electrical cables and wires, Glass and many ceramics, Dry air and Paper.
Semiconductors:
Semiconductor, any of a class of crystalline solids intermediate in electrical conductivity between a conductor and an insulator. Semiconductors are employed in the manufacture of various kinds of electronic devices, including diodes, transistors, and integrated circuits. They are having probable future, the key elements of the majority of electronic systems including communications with data-processing, consumer, and industrial-control equipment.
Semiconductor materials are useful by their behavior which can be easily manipulated by the addition of impurities is known as doping. Semiconductor conductivity can be controlled by the electric or magnetic field, by exposure to light or heat, or by the mechanical deformation of a doped mono crystalline grid; thus, semiconductors can make excellent sensors.
