Introduction

Now we are almost at the verge of finish line of our course. Let us now reminisce what have we studied so far. Let us cultivate the purpose of our study. One part of achievement of our study is of course to know the nature and the natural law and how technology has been developed on these laws to make our lives easier. But the other part of our goal is to be socially responsible towards proper utilization of electrical energy. Society expects that engineers should understand the technology at work around us. In this chapter we shall conclude our study by knowing the basic electrical technology associated with our domestic and social lives. We hope we shall be able to understand and shall make awareness among others as a responsible engineer.

Cables and Wires

Electrical cables are made of wires. Two or many wires twisted or running side by side make a cable. The wires are made of Ohmic conductors, mainly copper or aluminium, to carry the current. To carry more amount of current we need less resistive wires in order to maintain a reasonably low I2R loss. To reduce the per unit length resistance of a wire we need to increase the diameter of the wire. In short, for higher current rating of a wire we must have more amount of conductive metal. The overhead cables are naked conductors. But the underground cables or overhead cable in densely populated areas are generally covered by non-conducting insulation. The insulators are dielectric materials, usually polyurethanes; prevent two wires to get short circuited.