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, Volume 3 (Google eBook)

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American technical society, 1916 - Science
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Page 31 - Here it is seen that the maximum amount of light is given off at an angle of about 503 from the vertical, the negative carbon shutting off the rays of light that are thrown directly downward from the crater. If alternating current is used, the upper carbon becomes positive and negative alternately, and there is no chance for a crater to be «» formed, both carbons giving off the same amount of light and being consumed at about the same rate. The light distribution curve of an alternating-current...
Page 170 - L will glow for one moment and be dark the next. At the instant when the voltages are equal in pressure and phase, L will remain dark; but when the phases are displaced by half a period, the lamp will glow at its maximum brilliancy. Since the flickering of the lamp is dependent upon the difference in frequency, the machines should not be thrown in parallel while this flickering exists. The prime mover of the incoming machine must be brought to the proper speed; and the nearer machine N approaches...
Page 135 - It has been found that the best results are obtained when the tension in the driving side of the rope is only 3 to 4 per cent of the breaking strength.
Page 229 - ... be practically in phase with the potential difference across its terminals. The field produced by the coarse-wire coil is directly proportional to the current flowing through it at any instant. Hence, the couple acting on the fine-wire coil is proportional at a given instant to the product of these two fields ; so that the reading of the instrument, which depends on the mean value of the couple, will be proportional to the mean power, and, by providing the instrument with the proper scale, it...
Page 125 - SELECTION OF A MACHINE. The voltage, capacity, and type of machine are dependent upon the system to which it is to be connected, and the purpose for which it is to be utilized, but there are certain general features which should be considered in every case. Construction. This should be of the most solid character and guaranteed first-class in every respect, including materials and workmanship. Finish. A good finish is desirable, since it is likely to cause the attendant to take greater care of the...
Page 110 - ... so as to render it translucent. If the light falling on one side of this screen is in excess, the translucent spot will appear dark on that side of the screen and light on the opposite side. Care must be taken to see that the two sides of the screen are exactly alike, otherwise there will be an error introduced in using the screens. It is well to reverse the screen and check readings whenever a new lot of lamps are to be tested. When the light falling on the two sides of the screen is the same,...
Page 56 - anti-parallel feeding. Fourth, Conical " " " In the cylindrical conductor, parallel-feeding system, the conductors, A, B, C, D, Fig. 33, are of the same size throughout and are fed at the same end by the generator. The voltage is a minimum at the lamps E and a maximum at the lamps F; the value of the voltage at any lamp being readily calculated. By a conical or tapering conductor is meant a conductor whose diameter is so proportioned throughout its length that the current, divided by the cross-section...
Page 108 - Light Standards. Inasmuch as sources of light are compared with one another in photometry, we must have some standard, or unit, to which all light sources are reduced. This unit is usually the candle-power and the rating of most lamps is given in candle-power. While the candle-power remains the unit and is based on the standard English candle, other light standards have been introduced and are much more desirable. The English Candle. The English candle is made of spermaceti extracted from crude sperm...
Page 62 - Transactions of the Illuminating Engineering Society: 1908. The same authorities give the following useful data : To determine the watts required per square foot of floor area, multiply the intensity of illumination desired by the constants given, as follows: INTENSITY CONSTANTS FOR INCANDESCENT LAMPS Tungsten lamps rated at 1.25 watts per horizontal candle-power; clear prismatic reflectors, either bowl or concentrating; large room; light ceiling; dark walls; lamps pendant; height from 8 to 15 feet...

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