Journal of the Illuminating Engineering Institute of Japan

The present paper is to be regarded as the continuation of the previous paper published in this Journal, Vol.7, No.2 (August 1, 1923). In this paper, the author describes the newly observed phenomena in electric incandescent lamps which was not dealt with in that contribution.

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In this paper, the relation between life and impressed voltage of 100 volt, 10 candle power, incandescent vacuum tungsten lamp was mainly studied with the lifecandle power, life-efficiency and life-filament resistance relation.
About two thousands of lamps manufactured in 1918 by two representative lamp manufacturing companies at that time in Japan were subjected to this test.
The results show that the well known life-voltage relation, L V^a=Constant, can not be applied to these lamps: that is, the logarithms of life and voltage do pot consist any straight line relation but must be regarded as a branch of hyperbola (see-fig-8) and this equation gives lives from ten to twenty percent deviated from the experimental for the test voltage between 100 and 150 volts.
Moreover, when this form of life-voltage relation be adopted, despite of these errors, the index number 14 now commonly in use should be changed into from 11 to 12.

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