File:The fireside university of modern invention, discovery, industry and art for home circle study and entertainment (1902) (14776559234).jpg

Identifier: firesideuniversi01mcgo (find matches)
Title: The fireside university of modern invention, discovery, industry and art for home circle study and entertainment
Year: 1902 (1900s)
Authors: McGovern, John. (from old catalog)
Subjects: Science
Publisher: Chicago, Union pub. house
Contributing Library: The Library of Congress
Digitizing Sponsor: The Library of Congress

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gth. Ordinary irontelegraph wire measures about 13 ohms to the mile. Now con-nect our Standard Cell—one volt—through one ohm Resistanceand we have a Current of one ampere. Unit Electro-MotiveForce (volt) through unit Resistence (ohm) gives unit of Cur-rent (ampere). If we want to carry only a small Current for along distance, we do not need to use large cells, but many ofthem. We increase the pressure or voltage by increasing thenumber of cells set up in series. If we have a wire of givenlength and Resistance and find we need 100 volts to force theright amount or strength of Current through it, and the Electro-motive Force of the cells we are using is one volt each, it willrequire 100 cells. If we have a battery that has an Electro-Motive Force of two volts to the ceil, as the storage battery has,fifty cells would answer. If we want a very strong Current ofgreat volume, so to speak, for electric light or power, and use agalvanic battery we would have to have cells of large surface
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MICHAEL FARADAY, F. R. S , D. C. L. ELECTRICITY. 49 and lower Resistance both inside and outside the cell. WhenDynamos are used they are so constructed that a given numberof revolutions per minute will give the right voltage. In fact,the Dynamo has to be built for the amount of Current thatmust be delivered through a given Resistance. The same holdsgood for a Dynamo as for a galvanic battery. If any one factoris a fixed one we must adapt the others to that one in order toget the result we want. Why is a mention of Resistance especially important ? Because all electrical operations in heating, cooking andlighting must be conducted on that line. All houses servedwith wires from a power-house may have radiators andcooking-ranges, and heat for such purposes is furnished in manyof the great residences of the country. This heat has the ad-vantage of being without odor, and making no ashes to empty,or dust to gather on furniture. It has the disadvantage, alongwith other so-called radiators o

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