98 



KENNELLY AND VELANDER— POTENTIOMETER 



jX = jMw is the mutual reactance included between / and b. M 

 denotes the mutual inductance between the primary winding and the 

 part bl of the secondary, and oj = 27r/, is the angular velocity (in 



Fig. I. Simplified diagram of connections, showing the rectangular poten- 

 tiometer P arranged for exploration of the potential distribution over the 

 working circuit IV. 



radians per second) of the impressed frequency /, in cycles per 

 second. 



The oscillator also supplies current to an associated working cir- 

 cuit W, containing the apparatus in which the distribution of plane- 

 vector^ a-c. potential is to be explored. A tuned vibration gal- 

 vanometer, VG, enables a potential balance to be obtained between 

 a selected pair of terminals on the working circuit, and the adjust- 

 able taps on the potentiometer circuit, so as to secure the relation 



Ua 



■■Ip(R-\-jX), r.m.s. volts Z (2) 



whereby the p.d. at the terminals, say A and B, can be evaluated in 

 terms of the calibrated constants R and X of the instrument, and 

 the measured potentiometer current Ip, taken at standard phase. If, 

 however, another p.d., say U ^c, for instance, across a standard re- 



3 A planevector may be defined as a geometrically directed complex 

 quantity in a plane of reference, and subject to the laws of complex arith- 

 metic, as distinguished from a vector which is subject to the laws of vector 

 arithmetic. In this paper the term "vector" is used as an abbreviation of 

 " planevector." 



