The Library of Work and Play: Electricity and Its Everyday Uses

One day Harold expressed a desire to see the dynamos, five miles away, which furnish the electric light in our apartment. So I told him to invite his best friend to accompany us and we would go. When we were some distance from the station the boys noticed the very tall chimneys and inquired why tall chimneys were needed for dynamos. I explained that the dynamos were run by steam-engines, and steam-engines required the burning of coal. "Oh!" said Ernest, Harold's friend, "I read in the paper that electricity is the rival of steam and is going to drive out the steam-engine." I suggested that we were about to see some steam-engines driving electricity out of that power station. But more seriously, I explained that steam-engines were used for many years as locomotives to draw the trains on the elevated railroads of New York City, and when at last they were displaced by electric trains some people thought that it was a case of electricity driving out steam, whereas what had really happened was that the steam power for running those trains had been concentrated at a central station, and its power was merely transmitted to the trains by means of electricity. The trains were, therefore, run by steam power quite as much as ever. In like manner, the surface cars of New York a few years ago were run by a cable, which was merely a very long belt used to transmit to the cars the power of steam-engines located at a central station. When they were changed to electric cars, electricity became the successful rival of nothing else than a twisted wire cable. The cars still run by steam power as before, but that power is transmitted by electricity instead of the discarded cable. Steam has driven out the horse as a power for drawing street cars, and electricity has enabled us to gather all the steam engines into central stations, where now they are furnishing the power for moving surface, elevated, and subway cars for street traffic, as also trains for suburban travel. Central station steam-engines are producing a vast amount of power, distributed all over the city by means of electricity, for doing a great variety of work and for furnishing electric light and heat, all of which we shall presently study. "Just before we go into this central station, can you tell me how the elevator is run in our apartment house?" "It is an electric elevator," said Harold. "And where does the electricity come from?" I inquired. "Well, I know that it comes from the street mains, but do they come from this power station?" "Yes," said I, "and we will now go in and see the steam-engines which lift you up stairs many times each day by sending electricity to run that elevator. If you choose to do so, you may claim for purposes of discussion that your elevator is run by steam." As we entered the building we came first to the dynamo room and both boys noticed that the tone which met their ears was that which I had produced for them in the telephone the night before. "I shall try to show you before we get through," I said, "that these dynamos are doing something which makes iron pulsate sixty times a second and that that is the cause of the pitch of this tone. But let us begin with the coal which is the source of all this power.

Dettagli