as Radiators in Wireless Telegraphy. 

 Table IX. 



695 



1 



Number 

 of turns 

 on Coil. 



Power taken 

 up in Arc 

 in watts. 



Frequency 



of 

 Oscillations. 



Secondary 



Current in 



miliiamperes. 



5 

 10 



2495 

 1537 



162,000 

 99,600 



27-4 

 214 



The increase in the number of turns by increasing the 

 inductance lowers the frequency of the oscillations, and this 

 lowers the power taken up in the arc, and therefore the 

 secondary current is reduced roughly in proportion to the 

 decrease in frequency. In all the above experiments the 

 Poulsen arc was used as a generator of undamped oscillations. 

 It was considered desirable, however, to compare the effects 

 obtained in this case with those when using a spark method 

 of exciting intermittent oscillations. 



The large square coils were pkiced vertical and facing each 

 other in positions (A.A.) and at 68 feet apart. They were 

 tuned to a frequency of 162,000. Oscillations were then 

 excited by an arc and a spark and the primary and secondary 

 currents measured and volt amperes given to the generator 

 in each case, as follows : — 



Table X. 



Generator. 



Volts. 



Amperes. 



Volt 

 amperes. 



Primary | Secondary 

 Current in Current in 

 amperes. , miliiamperes. 



Spark 



Arc 



122 



260 



2-6 

 8-0 



31-7 

 2080 



2-15 

 5-4 



0-56 

 21-0 









Roughly speaking, therefore, 70 times more power was being- 

 expended on the arc than on the induction-coil used to 

 create the spark, but the secondary current only increased 

 some 38 times. 



This seems to indicate that the intermittent spark method 

 of exciting the oscillations is not inferior but rather superior 

 in efficiency to the arc method, for the particular purpose 

 here considered. 



The conclusions to be drawn from this preliminary set of 

 3 A2 



