514 M. I. P u phi— Electrical Oscillations of 



IV. On the Effect of Iron upon Resonance and the Relation 

 between this Effect and the Frequency. 



Experiment 1. — A. few iron wires were then introduced into 

 the inertia coil and the secondary circuit was tuned To 

 my great surprise, I found that now the upper harmonic 

 maximum had disappeared and the maximum rise had dimin- 

 ished quite perceptibly, although the self-induction of the inertia 

 coil and therefore of the whole resonant circuit had been 

 considerably increased. Rut I must mention here that the 

 iron got so hot in a few seconds as to cause the fibre spool of the 

 inertia coil to smoke where the wire touched it. There was a 

 serious discrepancy between experiment and formula (15). 

 To bring out this discrepancy very strongly I placed all the 

 iron wire into the inertia coil (about 500 wires, each 40 cm long 

 and l mm in diameter). On tuning the circuit it was found thft 

 the maximum potential was reached at considerably smaller 

 capacity and that the rise of potential was incomparably smaller 

 than in the previous case. Table II gives the experimental 

 data, the curve in tig. 5 was plotted from this table. The 

 frequency was maintained nearly the same as in the previous 

 experiment, namely 875 complete periods per second. 





Table II. 





Capacity in 

 10~ 7 Farads. 



Difference of potential in 

 the condenser in Volts. 









35-5 



0-5 





39-5 



1-0 





43- 



1-5 





48- 



2 





54- 



2-5 





60' 



3-0 





62- 



3'5 





er 



4'0 





58- 



5-0 





52- 



6-0 





45- 



In the experiment (described in my last paper) with our 

 large alternator giving 100 periods per second I obtained with 

 similar inertia coil and the same iron wire a rise from 60 to 

 900 volts. In this experiment with four times the frequency 

 I expected to get nearly four times the rise and instead of that 

 there was hardly any rise at all. I inferred, therefore, that 

 the presence of iron in all probability diminishes at higher 

 frequency the rise of potential due to resonance. 



To investigate the relation between this damping of the iron 

 and the frequency I substituted for the small alternator our 



