Mechanical energy is transformed into electricity because in this form it can be conducted very readily from a convenient place of generation or source of power, such as a waterfall, to any spot within a reasonable distance and there be utilized as heat, light, or power.

Electric heating is only practicable when it is desirable to use heat for a short time at a certain point. In small quantities electric heat is used in cookers, welding processes, foot-warmers, cigar-lighters, etc. The advantage of this form of heat is that it is free from fumes, odor, and noises; its disadvantage is that it is too expensive for general heating. Electricity, when consumed in large quantities in a special electrical furnace, produces a very high temperature - ordinarily as high as 3500° C. - without difficulty, while in the case of a furnace used for smelting metals by the burning of coke under a forced draught, the temperature hardly ever exceeds 2000° C.

The practical use of electricity gives employment to a great many people. The various types of electrical work include over two hundred occupations. Four types of electrical work will be described in this chapter: (1) electrical apparatus work; (2) inside wiring; (3) outside wiring; and (4) power station work.