Insulator

Insulator or insulating material such as glass, mica, and rubber do not easily create free electrons nor allow the flow of free electrons. Chemical­ly, it is the atom's valence band electrons that bond with other atoms' valence band electrons to create molecules and compounds. The maxi­mum number of valence band electrons that can be shared between atoms is 8. Materials in the periodic table of elements with more than 4 valence band electrons are considered natural insulators. These atoms do not easi­ly give up their electrons to create free electrons.

Electrically, insulators do not allow free electrons to be created with­in the insulating material; moreover, insulators do not allow external free electrons to enter and flow through the insulating material. Insulating materials play a significant role in electricity and electronics. Insulating material is needed to separate conductors, for example, insulation sur­rounding a copper wire. Also, insulation may be an integral ingredient of an electronic component.

It is often desirable that electricity be prevented from flowing, or that some substance be inserted between two conductors to prevent current passing from one to the other. Materials that have this ability are called insulators. A typical example of an insulator is the rubber which is used as a covering for electric wires. Other examples of insulators in everyday use are the glass insulators in power line poles, the bakelite panels used in electronic equipment, and the porcelain knobs to support house wiring. Insulators are really just very poor conductors of electricity because they are made of materials which offer a very high resistance to current flow. Table II lists a number of familiar substances which are used as insulators in electricity and electronics.

Perfect Insulators and Perfect Conductors: It should be noted that there is no such thing as a perfect conductor, or a perfect insulator. All materials through which electricity moves offer some resistance to the movement of the electrons. All materials will permit electricity to flow through them; but those which are called insulators permit very little current to pass through them, even though a high voltage has been applied.

Use of Insulators and Conductors in Electric Circuits: An electric circuit consists of a conductor, or conductors, which are connected to a source of electromotive force so that current will move through them. Insulators are in­stalled whenever it is necessary to prevent current leaving the desired path through the circuit and taking some other, undesired, path.

Questionnaire:

• What is insulator? Explain.