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sexta-feira, 21 de outubro de 2011

O nascimento da lampada eletrica: 21/10/1879

Thomas Alva Edison apresenta seu invento ao repórter do New York Times, que desconfiado colocou um subtítulo assim redigido: Conflicting Statements As To Its Utility
 Parece que a lâmpada elétrica já deu o que tinha de dar. Vamos para o seu final...
 Paulo Roberto de Almeida

This Day in History
The New York Times, October 21, 1879

Edison's Electric Light

Conflicting Statements As To Its Utility

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There was no lack of enthusiasm or of confidence about Mr. Edison as he greeted the Times reporter who entered his laboratory at Menlo Park, N. J., yesterday. The inventor, a short, thick-set man, with grimy hands, led the way through his workshop, and willingly explained the distinctive features of what he and many others look upon as an apparatus which will soon cause gas-light to be a thing of the past. The lamp which Mr. Edison regards as a crowning triumph is a model of simplicity and economy. In the lamp the light is emitted by a horseshoe of carbonized paper about two and a half inches long and the width of a thread. This horseshoe is in a glass globe, from which the air has been as thoroughly exhausted as science is able to do. So good a vacuum is produced that it is estimated that at the utmost no more than a one-millionth part of the air remains. The operation of pumping lasts one hour and a quarter. At the ends of the carbon horseshoe are two platinum clamps, from which platinum wires run outwardly through a small glass tube contained within a larger one leading out of the glass globe. The small tube contains air. Within it the platinum wires are met by two copper wires connecting with the conductors of the electricity. The air is left in the small tube, because otherwise the copper wires would be fused by the electric current. The carbonized paper is capable of being made incandescent by a current of electricity, and while it allows the current to pass over it, its resistance to the heat is strong enough to prevent it from fusing.
The first place visited was the room in which the furnace for carbonizing the paper is situated. The furnace is of the ordinary pattern, and on the coals rested a horseshoe mold, in which the bristol board to be charred was placed. Over each horseshoe a piece of tissue paper was placed and the whole was washed until all the material of the card-board, except the carbon, was taken away. When the filaments were taken from the mold they resembled pieces of black thread. The particles hung tenaciously together, however, and the black horse-shoe was easily placed in the platinum clamps of the globe of the lamp. The exhausting of the air takes place after the carbon is put in position, and when this is done the lamp is complete. "As there is no oxygen to burn," said Mr. Edison, "you can readily see that this piece of carbon will last an ordinary life-time. It has the property of resisting the heat of the current of electricity, while at the same time it becomes incandescent, and gives out one of the most brilliant lights which the world has ever seen. The cost of preparing one of these little horse-shoes of carbon is about 1 cent, and the entire lamp will cost not more than 25 cents." Here the inventor gave a practical illustration of his invention. He was standing just under an ordinary gas chandelier in which two of his lamps were burning. He took one of the lamps out, and it appeared simply as a glass globe. He placed it back in the burner, and immediately a brilliant horse-shoe of golden light illuminated the globe. Mr. Edison then, by turning a screw in the lamp, brought the light down to a spark, turned it off completely, as gas can be turned off, and turned it on again to a brilliant incandescence by a twist of his fingers. He certainly demonstrated that in his own laboratory at Menlo Park, the electric light is as obedient to his will as the gas light is to the general public. The light from each lamp is of about the power of an ordinary gas-jet, but Mr. Edison claims that by increasing the electricity, he can raise the power to 15 gas-jets.
Eighty-four lights are burning night and day in the laboratory, and they are all supplied with electricity by an 80-horse-power engine, which is stationed in the basement of one of the buildings. This engine, in addition to feeding these lamps, furnishes the motive power for all the machines in the laboratory, and at night feeds the electric lights which have already been erected in Menlo Park, in anticipation of the proposed grand illumination. The wires which are to convey the electricity to the lamps for the grand display are to be above ground, so that all spectators can see and investigate them. They will lead directly from the lamps to the generator in the laboratory, and any person can trace them from point to point.
From the furnace-room Mr. Edison conducted the reporter to the room in which his lamps are made, and where the air is exhausted from them. In this room, also, is Mr. Edison's machine for regulating the pressure of the electricity as it passes to the different lamps throughout his laboratory. This machine consists of a series of coils of copper, over which the electric current is continually passing, and each coil is connected with a series of lamps. If the pressure is too great on any series of lamps it is at once shown by the coil representing that series, and can be regulated in an instant. In this room, also, the carbonized paper is placed in the globes, and the lamp is completed. It is Edison's pet room, and here he spends most of his time when not engaged in studying out new inventions.
It has been asserted by some persons who are supposed to be conversant with the subject of electricity that in order to furnish lights for houses in this City a copper coil as large as an ordinary barrel would be required as a conductor from the central station to the different houses in two or three blocks. Regarding this, Mr. Edison said: "The size and amount of conductors for carrying electricity for lighting purposes depends, of course, upon the distance to which the electricity is to be carried. If I have to carry it 10 miles my conductor must be larger than it must be if I have to carry it 10 feet. My idea is to have central stations to cover, say a square of three or four blocks. The pipes containing the wires on a street, if this idea is carried out, will not exceed in size the circumference of your arm. They will be laid under the flag-stones just at the edge of the sidewalk, as gas-pipes are now laid."
"What will be the cost of these conductors," asked the reporter.
"The cost, compared to gas-pipes, will be very small, and there is very little chance of their getting out of order. The wire itself, which will convey the electricity, will be an ordinary No. 9 telegraph wire, the same wire that you see in use every day by the Western Union Company. That is as near the size of a barrel as I intend to get."
"How will the light be distributed?"
"Precisely as gas is now distributed. You see that I can turn that burner off entirely if I wish to; I can lower it or I can raise it, just as you can lower or raise a gas jet. Our electricity will go from our central stations just as gas flows from the meter. Whether the company will charge for the light according to the amount of electricity which each consumer uses, or whether so much a month will be charged to each consumer I cannot say. That is a question which the company will determine when the electric light is introduced."
"Do you intend to illuminate Menlo Park on New Year's Eve?"
"Not for the public as soon as that. Menlo Park is now illuminated every night to a certain extent. All the lamps that we have on hand are lighted nightly, but we cannot give the grand display that I intend to give until we have more lamps. You can say this, however, that the electric light is perfected, and that all the problems which have been puzzling me for the last 18 months have been solved. I expect to have every house here lighted, and a number of street-lamps going within 10 days. When I once get the light started, I shall keep them burning night and day for at least two weeks, in order to make a time test of my carbon. I believe that it is practically infusible, and I have confirmed my belief by experiments here in my laboratory for several weeks, but I want the public to believe it from their own knowledge, and the only way to make the public believe it is to show it to them. I think that my carbonized paper is the only substance which is capable of becoming thoroughly incandescent, and at the same time of offering to the current of electricity sufficient resistance to prevent it from melting away. The vacuum in the globe, of course, offers no oxygen of any consequence to burn; but the intense heat generated by the electricity would destroy any other substance than this carbonized paper. There is absolutely nothing there to fuse. It is carbon, pure and simple, and no machine known to this age can generate enough electricity to destroy it."
"Have any electricians responded to your invitation to see you and investigate your method of lighting by electricity?"
"No electricians have been here yet, nor are there likely to be any here. Electricians are a very scarce article in this country, although there are many persons here who call themselves electricians. They don't come here, because they know that if they do they will be convinced that my light is at last a perfect one. I am glad they don't come. Practical men, with experience, and what I call 'horse sense,' are the best judges of this light, and they are the men whom I like to welcome to my laboratory."

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