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. In this post, we will briefly talk about Conductors & Insulators to find out how they differ.
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 a 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.
Insulators are substances that 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.