TATE AND FOOTE I ANODE FALL OF POTENTIAL 



483 



surrounding space or it does not. If We first assume that the 

 probe wire, with a small current flowing through it, does acquire 

 the potential of the surrounding space, or anode glow, then the 

 power supplied to the anode by the main discharge current may 

 be obtained by using the voltmeter reading. The voltmeter 



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Volt meter Method 

 Fig. 1. Diagram of connections 



readings are much smaller than the electrometer readings. 

 Hence on the above assumption less power is developed at the 

 anode while the voltmeter is connected. Since the potentials 

 of the anode and cathode are fixed in the present experiment, 

 the potential of the probe wire and anode glow must rise dur- 

 ing the time the voltmeter is connected. The potential dif- 

 ference between the probe and cathode increases and, the main 

 discharge current remaining constant, the difference in power 

 developed at the anode in the two cases of electrometer and 





