Every substance, even air, will conduct an electrical current if enough voltage is applied to it, but the word “conductor” normally is used for materials that allow current flow with little resistance.
The most common conductor is copper. It’s used in virtually all the wiring that connects automotive components together. The heavier the current a conductor has to carry, the heavier the gauge or thickness of the wire.
Materials that don’t conduct current easily are insulators. The plastic covering on a wire, and the ceramic portion of a spark plug are good insulators.
Conductors
In science and engineering, conductors are materials that contain movable charges of electricity. When an electric potential difference is impressed across separate points on a conductor, the mobile charges within the conductor are forced to move, and an electric current between those points appears in accordance with Ohm's law. While many conductors are metallic, there are many non-metallic conductors as well. See electrical conduction for more information on the physical mechanism for charge flow in materials.
Under normal conditions, all materials offer some resistance to flowing charges, which generates heat. Thus, proper design of an electrical conductor includes an estimate of the temperature that the conductor is expected to endure without damage, as well as the quantity of electrical current. The motion of charges also creates an electromagnetic field around the conductor that exerts a mechanical radial squeezing force on the conductor. A conductor of a given material and volume (length x cross-sectional area) has no real limit to the current it can carry without being destroyed as long as the heat generated by the resistive loss is removed and the conductor can withstand the radial forces. This effect is especially critical in printed circuits, where conductors are relatively small and the heat produced, if not properly removed, can cause fusing of the tracks.
Non-conducting materials lack mobile charges and are called insulators. A material can be an electrical conductor without being a thermal conductor, although a metal can be both an electrical conductor and a thermal conductor. Electrically conductive materials are usually classified according to their electrical resistance; ranging from high to null resistance, there are semiconductors, ordinary metallic conductors (also called normal metals), and superconductors.
Insulator - Definition
An Insulator is a material or object which resists the flow of heat (thermal insulators) or electric charge (electrical insulators).
Electrical insulator
The term electrical insulator has the same meaning as the term dielectric, but the two terms are used in different contexts.The opposite of electrical insulators are conductors and semiconductors, which permit the flow of charge. Semiconductors are strictly speaking also insulators, since they prevent the flow of electric charge at low temperatures, unless doped with atoms that release extra charges to carry the current). However, some materials (such as silicon dioxide) are very nearly perfect electrical insulators, which allows flash memory technology. A much larger class of materials, (for example rubber and many plastics) are "good enough" insulators to be used for home and office wiring (into the hundreds of volts) without noticeable loss of safety or efficiency.
High voltage insulators
High voltage insulators used for high voltage power transmission are either porcelain insulators or composite insulators. Porcelain insulators are made from clay, quartz or alumina and feldspar. Alumina insulators are used where high mechanical strength is a criterion. In recent times there is a shift towards composite insulators which have a central rod made of fibre reinforced plastic and outer weathersheds made of silicone rubber or EPDM. Glass insulators were, and in some places are still used to mount electrical power lines. Most insulator manufacturers stopped making glass insulators in the late 1960's, switching to ceramic materials. Composite insulators are less costly, light weight and have excellent hydrophobic capability and hence can be used in polluted areas.
Low voltage insulators
Insulating materials such as PVC (polyvinyl chloride) are used to minimize the possibility of a person coming into contact with a 'live' wire. Some appliances such as electric shavers and hair dryers are doubly insulated to protect the user. They can be recognized because their leads have two pins).
Double insulation, requires that cables have basic and supplementary insulation each of which is sufficient to prevent electric shock. Usually, the internal electrical components are totally enclosed in an insulated packaging (usually of plastic) which prevents any contact with live parts.
Source: CDX Global & Wikipedia - en.wikipedia.org
