Bulletin of the Bureau of Standards Volume 3

Bulletin of the Bureau of Standards Volume 3

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This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1907 edition. Excerpt: ...a second observer read the photometer, and a third observer increased the speed gradually and noticed when the filament touched the bulb. It is seen that as each loop touched, a decrease in candlepower resulted, but it was impossible to say a priori how much the intensity would decrease when the filament touched. These various results are not surprising when we consider the effect of a contact of the filament with the bulb. On touching the bulb the filament is cooled, and so a decrease in candlepower is to be expected. Moreover the amount of the cooling, and consequently the decrease in candlepower, depends upon whether the filament touches in only one point, or whether it lies against the glass for an appreciable part of its length, so that the decrease in candlepower is not always the same when a filament touches the bulb. Independent evidence of the cooling of the filament and the con-0 sequent decrease in candlepower is afforded by a study of the current values. Although a change in voltage of from 100 to 110 volts produced an increase in resistance of only 2 parts in 1000, yet the cooling due to the contact of a small part of the filament with the bulb was sufficient to increase the current appreciably, in one case the change amounting to 1 part in 1000. But although the resistance changes are indicative of the cooling, quantitative relations could not be deduced because of the very complicated nature of the phenomenon. It would seem that the double filament lamp would probably show a greater decrease in mean horizontal candlepower due to bending than any other type of lamp made in the United States. The two loops of which the filament is composed are long and slender, and being unsupported are susceptible to centrifugal forces. Moreover the...show more

Product details

  • Paperback | 172 pages
  • 189 x 246 x 9mm | 318g
  • Rarebooksclub.com
  • Miami Fl, United States
  • English
  • black & white illustrations
  • 1236493354
  • 9781236493354