172 



Introduction to the Study of Science 



The average candle power of the carbon filament is 13.2, or 

 2.8 less than the commercial rating. The average candle 

 power of the tungsten, sold as a 16 candle power lamp, is 16.5, 

 or .5 more than its commercial rating. Late improvements 

 have increased the normal life of the tungsten filament and 

 its candle power, and have decreased the amount of electricity 

 required per candle power. 



In general, the tungsten filament lamp consumes about one 

 third less electric energy than a carbon lamp of the same candle 

 u power and lives twice as long. This 



makes for the reduction of the cost of 

 electric current for the consumers, and 

 makes possible a larger use of electricity 

 for lighting. 



67. Wiring a house. The diagram 

 (Fig. 48) illustrates the chief features of 

 a wiring system for electric lighting. The 

 main switch is placed in the basement or 

 any convenient location for connection 

 with the main service wires and the house 

 wires. It is so located as to enable one 

 to cut off the electric current outside the 

 meter. The main switch is usually a 

 knife switch with cartridge fuses or fuse 

 plugs. The fuses protect the house lamps 



P.P.- 



n 



s 



n 



w w 



FIG. 48. General plan 

 for wiring house with in- 

 candescent lamp connec- 

 tions (L), keys (K), main 



switch (S), fuse plug and occupants from injury in case of ex- 

 cessive pressure of the current, and from 

 fire in case of a short circuit in the house 

 system. The wires are sometimes run 

 through conduits of insulating and fireproof material. Inside 

 switches are conveniently located in the circuit to control the 

 lighting. The sockets in which lamps are placed are generally 

 provided with fuses which withstand a limited pressure and 

 thus protect the lamp. The two main wires make possible a 

 complete circuit for the electric current (see page 328). 



(F.P.), and meter (M}. 

 Fuses (F) to protect lamps 

 from excess current are 

 located conveniently. 



