NO. 2 HISTORY OF ELECTRIC LIGHT — SCHROEDER 6^ 



multiple D. C. and A. C. arc lamps as more watts are lost in the 

 resistance ballast of the multiple D. C. lamp than are lost in the 

 reactance ballast of the multiple A. C. lamp. 



This reactance gives the A. C. lamp what is called a " power-factor." 

 The product of the amperes (7.5) times the volts (no) does not give 

 the true wattage (540) of the lamp, so that the actual volt-amperes 

 (825) has to be multiplied by a power factor, in this case about 65 per 

 cent, to obtain the actual power (watts) consumed. The reason is 

 that the instantaneous varying values of the alternating current and 

 pressure, if multiplied and averaged throughout the complete alter- 

 nating cycle, do not equal the average amperes (measured by an 

 ammeter) multiplied by the average voltage (measured by a volt- 

 meter). That is, the maximum value of the current flowing (am- 

 peres) does not occur at the same instant that the maximum pressure 

 (voltage) is on the circuit. 



THE FLAME ARC LAMP 



About 1844 Bunsen investigated the effect of introducing various 

 chemicals in the carbon arc. Wothing was done, however, until 

 Bremer, a German, experimented with various salts impregnated in 

 the carbon electrodes. In 1898 he produced the so-called flame arc, 

 which consisted of carbons impregnated with calcium fluoride. This 

 gave a brilliant yellow light most of which came from the arc flame, 

 and practically none from the carbon tips. The arc operated in the 

 open air and produced smoke which condensed into a white powder. 



The two carbons were inclined downward at about a 30-degree 

 angle with each other, and were of small diameter but long, 18 to 

 30 inches, having a life of about 12 to 15 hours. The tips of the 

 carbons projected through an inverted earthenware cup, called the 

 " economizer," the white powder condensing on this and acting not 

 only as an excellent reflector but making a dead air space above the 

 arc. The arc was maintained at the tips of the carbons by an electro- 

 magnet whose magnetic field " blew " the arc down. 



Two flame arc lamps were burned in series on no-volt circuits. 

 They consumed 550 watts each, giving an efficiency of about 35 lumens 

 per watt on direct current. On alternating current the efficiency was 

 about 30 1-p-w. By use of barium salts impregnated in the carbons, 

 a white light was obtained, giving an efficiency of about 18 1-p-w on 

 direct current and about 15-0 on alternating current. These figures 

 cover lamps equipped with clear glassware. Using strontium salts 

 in the carbons, a red light was obtained at a considerablv lower effi- 



