66 



ELECTRICAL MEASUREMENTS 



Combining (41) and (36a) and (42) and (37o) and assuming 

 that the same total current flows, /o = /, 



(43) 



(44) 



The results obtained by using these formulae are compared 

 with the experimental results in the following table. The agree- 

 ment is as good as the experimental accuracy warrants. 



TABLE SHOWING DISTRIBUTION IN A THREE-WIRE HIGH-FREQUENCY 

 AMMETER. ALL THREE WIRES IN SAME PLANE 



From the table it is seen that the changes in distribution are 

 practically confined to the frequencies between 100,000 and 

 1,500,000. That is, the range of frequencies in which the changes 

 of distribution occur is that used in radio-telegraphy. Extreme 

 effects of change in current distribution are shown in Fig. 30, 

 which applies to the seven-wire arrangement there shown. 



The Use of High Resistance Wires. The distribution errors 

 may be minimized by using wires of high resistivity, keeping 

 their lengths and diameters, and therefore their inductances, the 

 same. For example, suppose all the resistances in equation 

 (43) were increased to 30 times their original values, then 



111.6 + 0.363 X 10~ 12 X 



1.986). 



994.5 + 2.98 X 10~ 12 X /.' 

 Practically, the value of the radical is now determined by the 



