Electrical Conductors and Insulators

All materials are made up of atoms and there are millions of them which form the substance. An atom consists of 3 basic particles the protons, neutrons, and the electrons. The center of an atom is a dense area called the nucleus. The nucleus contains the positively charged protons and electrically neutral neutrons that contains most mass of the atom. The electrons are the negatively charged particles that surrounds the nucleus as a cloud. The electrons are bound to the nucleus by an electromagnetic force. A group of atoms collectively bound together are called as a molecule. An atom that contains an equal number of protons and electrons are electrically neutral. If the atom contains more number of electrons then it will have a negative charge, and if the atoms contains less number number of electrons it will exhibit a positive charge. A positively or negatively charged atom is known as an ion. When the atom loses one of its electrons and becomes slightly positive, it is called as a positive ion. When the atom gains an electron by picking up from the neighboring atom it becomes slightly negative, and it is called as a negative ion.

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The electrons of different types of atoms possess varying degrees of freedom to move around their nucleus. Some materials have their outer electrons that are loosely bound to their nucleus and are influenced by heat or electrical voltage. These materials give up electrons and allow them to move about when electrically attracted. Those unbound electrons that moves freely and leave the atom to the adjacent one are called as fee electrons. When an electrical voltage is applied to those materials, the free electrons under the action of an electrical field move from a lower potential to the higher potential. Those materials that allows the free flow of electrons when an electrical voltage is applied are called as conductors.

Some examples of conductors are copper, silver, aluminum, gold, brass, bronze, iron, steel, mercury, graphite, concrete etc.

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​Certain materials do not allow the transfer of electrons from one atom to another as they are firmly bound to their nucleus. Electrical voltage does not produce any current to pass through those materials. Those materials that consist of atoms which does not allow the flow of electrons when applying electrical voltage across it are called as insulators. These materials offers high resistance to the flow of current through it.

Some examples of insulators are glass, rubber, asphalt, porcelain, fiberglass, Teflon, paper, wood, cotton, quartz, diamond, air, oil, etc.

All conductors do not have the same level of conductivity and all insulators do not have the same level of resistance to the movement of electrons. Materials such as silver are better conductors and allows the passage of electrons than graphite or concrete.

Some materials show changes in electrical properties under different conditions. Materials such as glass or air are very good insulators at room temperature but becomes a conductor when heated to high temperatures. Metals are good conductors when at room temperature but become less conductive when heated. Most metals become extremely conductive when cooled under extremely low temperatures.

Conductance is the ability of a material to conduct electricity. Conductance is inverse of resistance. Conductance  = 1/ resistance. The SI unit of conductance is siemens.

The electrical resistance of an electrical element is the opposition to the passage of an electric current through that element. The unit used to measure the resistance of a conductor to the flow of current is called as ohm.

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