NO. 2 HISTORY OF ELECTRIC LIGHT SCHROEDER 93 



STANDARD VOLTAGES 



Mention has been made of no- volt service, 220-volt service, etc. 

 In the days of the carbon incandescent lamp it was impossible to 

 manufacture all lamps for an exact predetermined voltage. The 

 popular voltage was no, so ligliting companies were requested in a 

 number of instances to adjust their service to some voltage other 

 than no. They were thus able to utilize the odd voltage lamps 

 manufactured, and this produced a demand for lamps of various 

 voltages from 100 to 130. Arc lamps had a resistance (reactance on 

 alternating current) that was adjustable for voltages between 100 

 and 130. 



Similarly a demand was created for lamps of individual voltages 

 of from 200 to 260. The 200- to 260-volt range has simmered down 

 to 220, 230, 240 and 250 volts. These lamps are not as efficient as 

 the no-volt type and their demand is considerably less, as the no- 

 volt class of service for lighting is, with the exception of England, 

 almost universal. Thus no-volt service means 100 to 130 volts in 

 contra-distinction to 200 to 260 volts, etc. The drawn tungsten wire 

 filament made it possible to accurately predetermine the voltage of 

 the lamp, so now that the carbon incandescent lamp is a thing of the 

 past, there is no need for so many different voltages. Several years 

 ago standard voltages of no, 115 and 120 were recommended for 

 adoption by all the electrical societies in the United States, and practi- 

 cally all central stations have now changed their service to one of 

 these voltages. 



COST OF INCANDESCENT ELECTRIC LIGHT 



In the early '8o's current was expensive, costing a consumer on the 

 average about twenty cents per kilowatt hour. The cost has gradually 

 come down and the general average rate for which current is sold 

 for lighting purposes is now about 4^ cents. During the period 1880 

 to 1905 the average efBciency of carbon lamps throughout their life 

 increased from about one to over 2f lumens per watt and their list 

 price decreased from one dollar to twenty cents. The average amount 

 of light obtained for one cent at first was about five candlepower hours 

 and in 1904 it was increased to over thirty-six at the average rate 

 then in effect. The next year with the more efificient Gem lamp 44 

 candle-hours could be had for one cent. In 1906 the amount was 

 increased to 50 with the tantalum lamp and with the tungsten lamp 

 in 1907, even at its high price of $1.50, the amount was further 

 increased to 63. Since then the average cost of current has been 



