In little more than a century, electricity has become indispensable as our major energy carrier, both in industry and in everyday life. With the energy transition towards a low carbon economy, electricity’s role will continue to grow. At the core of every electrical installation are electrically conductive and insulative materials.
The difference between conductor and insulator
If the material will conduct an electric current, it is called a “conductor.” If the material will not conduct an electric current, it is called an “insulator.”
Insulating materials are therefore used as insulation for conductors by enclosing conductors, such as wires, in a layer of the insulation.
In electrical engineering, a conductor (or electrical conductor) is defined as an object or type of material that allows the flow of charge in one or more directions. Materials made of metal are common electrical conductors, as metals have a high conductance and low resistance.
In some materials, electrons move easily from atom to atom. In others, the electrons move with difficulty. And in some materials, it is almost impossible to get them to move. An electrical conductor is a substance in which the electrons are mobile. The best conductor at room temperature is pure elemental silver. Copper and aluminum are also excellent electrical conductors. Iron, steel, and various other metals are fair to good conductors of electricity.
In most electrical circuits and systems, copper or aluminum wire is used. Silver is impractical because of its high cost.
Some liquids are good electrical conductors. Mercury is one example. Saltwater is a fair conductor.
Gases are, in general, poor conductors of electricity. This is because the atoms or molecules are usually too far apart to allow a free exchange of electrons. But if gas becomes ionized, it is a fair conductor of electricity.
Electrons in a conductor do not move in a steady stream, like molecules of water through a garden hose. Instead, they are passed from one atom to another right next to it.
This happens to countless atoms all the time. As a result, literally trillions of electrons pass a given point each second in a typical electrical circuit.
You might imagine a long line of people, each one constantly passing a ball to the neighbor on the right. If there are plenty of balls all along the line, and if everyone keeps passing balls along as they come, the result will be a steady stream of balls moving along the line. This represents a good conductor.
If the people become tired or lazy and do not feel much like passing the balls along, the rate of flow will decrease. The conductor is no longer very good.
Insulators are materials that inhibit the flow of electrical current. The opposite of conductors, which allow electric particles to flow freely, insulators are implemented in household items and electrical circuits as protection. Thermal insulation is similar, but it constricts the flow of heat rather than electricity.
If the people refuse to pass balls along the line in the previous example, the line represents an electrical insulator. Such substances prevent electrical currents from flowing, except possibly in very small amounts.
Most gases are good electrical insulators. Glass, dry wood, paper, and plastics are other examples. Pure water is a good electrical insulator, although it conducts some current with even the slightest impurity. Metal oxides can be good insulators, even though the metal in pure form is a good conductor.
Electrical insulators can be forced to carry current. Ionization can take place; when electrons are stripped away from their atoms, they have no choice but to move along. Sometimes an insulating material gets charred, or melts down, or gets perforated by a spark. Then its insulating properties are lost, and some electrons flow.
An insulating material is sometimes called a dielectric. This term arises from the fact that it keeps electrical charges apart, preventing the flow of electrons that would equalize a charge difference between two places. Excellent insulating materials can be used to advantage in certain electrical components such as capacitors, where it is important that electrons do not flow.
Porcelain or glass can be used in electrical systems to keep short circuits from occurring. These devices, called insulators, come in various shapes and sizes for different applications. You can see them on high-voltage utility poles and towers. They hold the wire up without running the risk of a short circuit with the tower or a slow discharge through a wet wooden pole.
|Conductors allow free flow of|
electrons from one atom to another.
|Conductors do not allow free flow of|
electrons from one atom to another.
|Conductors conduct electricity||Insulators insulate electricity|
|The main function of a conductor is to provide a pathway between a voltage source and a load||The main function of an insulator is|
to block the energy
|Atoms of conductors are not able to|
hold onto their electrons tightly.
|Atoms of insulators have tightly|
|Ideal conductors have no resistance.||Ideal insulators have infinite resistance.|
|Good conductors are copper, aluminum, silver, iron, gold, aqueous solutions of salts, the human body, etc.||Common insulators are rubber, glass, ceramic, plastic, asphalt, pure water, etc.|