1905.] 



McCLELLAN— USE OF OSCILLOGRAPH. 



171 



necessary to have a non-inductive resistance in series with each 

 loop to cut down the current to a proper value. A non-inductive 

 shunt is also frequently used with the current loop. Fig. 4 pro- 



u 



vides an analysis of the quantities involved. Let E be the poten- 

 tial difference between A and B. Lagging behind this at an angle 

 a is the current in L(i) 3 . Also lagging behind E at an angle d 

 is the current in 2 (i 2 ). But the current through O x is the vector 

 sum of i and / or i . Now the angle, or rather the space on the 



plate equivalent to the angle, is of course the angle of phase 

 between t\ and i 2 and not between E and / 3 , as is frequently in- 

 ferred. It may approach in certain cases, but it is never the true 

 value. The angle desired, that is a, is given by the relation 



a=8+(p j r 0. (1) 



PROC AMER. PHILOS. SOC XLIV. l8o. L. PRINTED AUGUST I, I905. 



