Definition, Types and Characteristics of Insulator
Those substances which do not allow the flow of electrons from inside themselves are called good conductors of electricity. According to electronic theory, such substances which do not have free electrons about the external paths of the atoms, they are called good insulators or bad conductors of electricity. Their atoms always have four electrons in their last shell. Good conductors of electricity – Rubber, asbestos, asbestos, porcelain, PVC. Empire cloth etc.
Characteristics of a good conductor
• Specific resistance – A good insulator should have a specific resistance greater than 10¹² ohm centimeter.
• Moisture – The non-conducting material should not be affected by moisture or water.
• Permittivity – It is the ratio of the capacitance of a capacitor when its plates are impregnated with an insulating material and air.
• Dielectric strength – It is used to tell the difference between insulators. Dielectric strength is the maximum kilovolt per milliliter or volt per millimeter that a substance can hold without tearing itself.
• Mechanical strength – The mechanical strength of a good conductor should be good so that it is not affected by the weather.
• Temperature – The capacity of the conductor to bear the heat should be high.
Types of Insulators :-
Which of the insulators are divided into the following types.
• Solid Insulators :- Solid insulators are very heavy in weight and very strong. They are called solid conductors. They are kept in the category of strong insulators. For example, glass, marble etc.
• Soft Insulators :- Soft insulators are such insulators whose weight is less than that of solid conductors. And it is not called strong but soft nature. Soft insulators are called such as plastics, rubber etc.
• Liquid Insulators :- Liquid insulators are such insulators which have the property of flowing i.e. they are in liquid state. Like – Oil, Varnish etc.
Material Types of insulator
Bakelite
Or is a good conductor of electricity. It is a special type of plastic material. It is used for manufacturing switch folders, terminal boards, electrical wiring fittings, sockets, etc. It is heated and shaped according to the mould. Thus it takes the form of hard element.
Mica
It is a good conductor of electricity. Its dielectric power is very high. Moisture and fire have little effect on it. This is a mineral substance. At around 600ºC it starts to soften. It is used in power presses, in the middle of commutator segments and in condensers etc.
Rubber
To make the rubber hard, 5% sulfur, zinc oxide and red colored lead are added. The rubber thus prepared is called VIR Vulcanized Indian Rubber. From this, battery containers, rubber gloves, etc. are made.
Asbestos
It is used for making sheets. It is used for arc chamber of electric press, oven, electric kettle and circuit breaker. It is a mineral substance, which is not affected by acid.
Glass
It is a good transparent bad conductor. It is not affected by alkali, acid, moisture, oil, grease etc. Bulbs, Mercury arc lamps etc. are made by this. It is a rapidly degrading material. Its mechanical strength is low.
Fiber
It is a good conductor of electricity. It is of red colour. It is used for trapping in the slots of the winding. Its washers are also made. They are available in thickness from 1 mm to 12 mm.
Leatheroid paper
It is a paper of good dielectric strength. Its color is like green and some blackness. This is what comes in E class insulators. It is used to insulate the slot in the motor winding.
The outer electrons are very tightly bound inside the insulator, due to which they cannot move freely, that is, they cannot move. The connective bands in the insulator are completely filled. Whereas the driving bands are completely empty. The forbidden energy gap between the valence band and the conduction band is very large. Insulators are those materials in which the outer electrons are very strongly bound, so they cannot move. Those substances which do not have free electrons are called insulators or dielectrics. The largest barred energy gap is 6eV of diamond. Diamond is the worst conductor.