The Electric Light in Our Homes - Tapa blanda

This historic book may have numerous typos and missing text. Purchasers can usually download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1884 edition. Excerpt: ...acid, the so-called burning agent, and the pieces of metal consist, the one of zinc and the other of copper. There is continuous action between the zinc and the sulphuric acid, Current Produced by Primary Batteries very Costly, 101 provided the ends of the wires attached to the two pieces of metal are joined together, when a slight current of electricity passes; but if an incandescent lamp were placed between the two poles, no light would be visible, as the current would fall far short of the intensity required to make the carbon filament within the lamp white hot. It may, indeed, be taken for granted that no chemical battery is commercially suitable for the production of the current for electric light purposes; for though the battery might be made of much greater power than the one described above, the constant consumption of expensive chemicals and metals would make the light obtained very costly for even small installations, and the number of cells for running 10,000 lights from a centre, or from house to house, would from a commercial point of view be something appalling; and though electricity can also be obtained in a form of apparatus known as the thermopile, from heat, the currents which are now being used for electric lighting are, almost without exception, produced in so-called dynamo-electric machines (Fig. 57), and I will now proceed to explain as simply as possible how these machines do their work. I hold in my right hand a rod of ordinary iron which has no magnetic properties, and which is known technically as soft iron; in the other I have a length of copper wire, covered with India-rubber to insulate it, and made into a spiral form or helix. Fig. 57.--Dynamo Electric Machines. Through this wire is passing an electric...