224 Mr. W. H. Preece. Behaviour of Glow-Lamps [Mar. 26, 



Experiment 4. — Copper Centre (single). 



Filament. 



Shunt. 



Remarks. 



Volts. 



CO 



g 

 1 



Calculated 



resistance 



(hot). 



Calculated 

 E.M.F. 



Current in 

 milliamperes. 



Resistance. 







ohms. 



volts. 









RO 





140-4 





0-048 







90 



67 



134-3 



39-2 



1-12 



35,000 





100 



79 



126-6 



19 '0 



3-80 



5,000 



Faint blue. 











needle 





110 



90 



122-2 



••{ 



hard 



}■■ 



Strong blue. 











over 







90 



67 



134-3 



29-9 



0-88 



34,000 



Reversed the current through 















the filament and repeated 















the experiments. 



100 



•79 



126 6 



17 2 



3-32 



5.190 



Faint blue. 











needle 







110 



•90 



122-2 



••{ 



hard 



}'■■ 



Strong blue. 











over 







7. Lamp No. 9 was made with a double platinum plate, thus : — 



Fig. 2 



The following experiment shows that no perceptible difference was 

 observable : — 



