What is Conductor

Chapter Conductors

Teach Yourself Electricity and Electronics Third Edition Book
Pages 748
Views 8,772
Downloads : 12 times
PDF Size : 4.4 MiB

Summary of Contents

Teach Yourself Electricity and Electronics Third Edition Book

  • Sometimes oxygen atoms are by themselves; then we denote the molecule simply as O.Sometimes there are three atoms of oxygen grouped together. This is the gas calledozone, that has received much attention lately in environmental news. It is written O3.All matter, whether it is solid, liquid, or gas, is made of molecules. These particlesare always moving. The speed with which they move depends on the temperature. Thehotter the temperature, the more rapidly the molecules move around. In a solid, themolecules are interlocked in a sort of rigid pattern, although they vibrate continuously(Fig. 1-4A). In a liquid, they slither and slide around (Fig. 1-4B). In a gas, they are lit-erally whizzing all over the place, bumping into each other and into solids and liquidsadjacent to the gas (Fig. 1-4C).ConductorsIn some materials, electrons move easily from atom to atom. In others, the electronsmove 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 alu-minum are also excellent electrical conductors. Iron, steel, and various other metals arefair to good conductors of electricity.In most electrical circuits and systems, copper or aluminum wire is used. Silver isimpractical because of its high cost.Some liquids are good electrical conductors. Mercury is one example. Salt water isa fair conductor.Gases are, in general, poor conductors of electricity. This is because the atoms ormolecules are usually too far apart to allow a free exchange of electrons. But if a gas be-comes ionized, it is a fair conductor of electricity.Electrons in a conductor do not move in a steady stream, like molecules of waterthrough a garden hose. Instead, they are passed from one atom to another right next toit (Fig. 1-5). This happens to countless atoms all the time. As a result, literally trillionsof 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 theneighbor on the right. If there are plenty of balls all along the line, and if everyone keepspassing balls along as they come, the result will be a steady stream of balls moving alongthe 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.InsulatorsIf the people refuse to pass balls along the line in the previous example, the line repre-sents 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 areother examples. Pure water is a good electrical insulator, although it conducts somecurrent with even the slightest impurity. Metal oxides can be good insulators, eventhough the metal in pure form is a good conductor.Insulators11