The Fifteen Watt Tungsten Lamp

by Clair Elmore Anderson

Shot diagram for 15 watt lamps

III. CHARACTERISTIC CURVES.

Figure [1], Page 8, shows the variations of the candle power with the voltage, current and watts. Figure [II] shows the relation between candle power and the efficiency, watts per horizontal candle power, and also the variation of the candle power with the resistance.

An empirical formula for the candle power expressed as a function of the watts is cp = KW^x where K is a constant of the lamp and W denotes the watts. From the curve when cp = 5, watts = 11.1 and when cp = 15, watts = 17.5 dividing

cp₁/cp_a = KW₁^x/KW_a^x

substituting

5/15 = 11.1^x/17.5^x

and

log 3 + x log 11.1 = x log 17.5