Cyclopedia of Applied Electricity: A General Reference Work on Direct-current Generators and Motors, Storage Batteries, Electrochemistry, Welding, Electric Wiring, Meters, Electric Light Transmission, Alternating-current Machinery, Telegraphy, Etc, Том 1

American technical society, 1913

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Сторінка 86 - Required resistance : 150 :: (.010)' : (.022)' or, Required resistance = 150 X ,n 00^, = 30.99+ ohms. (•022) For a wire 400 feet long, we have, therefore, by direct proportion, Required resistance = r-57r7, X 30.99 = 6.88+. Ans. 6.88+ ohms. If a circuit is made up of several different materials joined in series with each other, the resistance of the circuit is equal to the sum of the resistances of its several parts. In calculating the resistance of such a circuit, the resistance of each part should...
Сторінка 357 - ... be thoroughly ventilated to the outdoor air, if possible, through a chimney or flue. There should be at least six inches air space on all sides of the transformer.
Сторінка 117 - The common unit of heat is the calorie, which is the amount oi heat necessary to raise the temperature of 1 gram of water through 1 degree Centigrade. By careful investigations it has been found that the joule is equivalent to .24 of a calorie ; that is, one joule of electrical energy when transformed into heat is equal to .24 calorie. Electrical energy may therefore be expressed in heat units by multiplying the number of joules by .24 ; that is, U=I* XHX «X.24 whare U is the heat in calories.
Сторінка 84 - As the area of a circle is proportional to the square of its diameter, it follows that the resistances of round conductors are inversely proportional to the squares of their diameters.
Сторінка 114 - ... twice that of the other, and send currents of equal strengths through each. The amount of heat developed in the wire of higher resistance will be twice that developed in the wire offering the lower resistance. The unit used to express the amount of mechanical work done is known as the foot-pound. The work done in raising any mass through any height is found by multiplying the weight of the body lifted by the vertical height through which it is raised; similarly, the practical unit of electrical...
Сторінка 286 - ... inch block must be fastened between studs or floor timbers flush with the back of lathing to hold tubing, and to support switches or fixtures. When this cannot be done, wooden base blocks, not less than %. inch in thickness, securely screwed to lathing, must be provided for switches, and also for fixtures which are not attached to gas pipes or conduit.
Сторінка 291 - Must be placed at every point where a change Is made in the size of wire (unless the cut-out In the larger wire will protect the smaller.) (c) Must be in plain sight, or enclosed in an approved cabinet, and readily accessible.
Сторінка 251 - The lower limit is specified for rubber-covered wires to prevent gradual deterioration of the high insulations by the heat of the wires, but not from fear of igniting the insulation. The question of drop is not taken into consideration in the above tables.
Сторінка 334 - Cables may be supported in approved junction boxes on two or more insulating supports so placed that the conductors will be deflected at an angle of not less than 90 degrees, and carried a distance of not less than twice the diameter of the cable from its vertical position. Cables so suspended may be additionally secured to these insulators by tie wires.
Сторінка 355 - Any circuit attached to any machine, or combination of machines, which develops a difference of potential, between any two wires, of over ten volts and less than 300 volts, shall be considered as a low-potential circuit...