in the Branches of a Wheatstone' 's Bridge. 



163 



broken. Imagine it to be so broken, and we have merely 

 the case of a divided circuit of two branches, each branch 

 containing two coils with impedance. To find the currents 

 in each branch independently we have 



in which I 1)3 denotes the current in the branches (I) and (3) 

 (fig. 1) and SJ the total impedance of these branches. 



Fig. 2.— General diagram, illustrating the currents and potential-dif- 

 ferences in the two branches of a divided circuit, each branch containing 

 two coils with impedance ; and showing the condition for zero current 

 in the galvanometer of a Wheatstone 's bridge. 



/. 



(4) 



* 



(5) 



jsr 



1/ / 



V 



K- 



Q 



*< 



\5 



;< 



\& 



te^e 



D 



■2* ' 



V 



^ '< 







The angle by which this current lags behind the impressed 

 E.M.F. ; OA,is 2l3 ll 



tan0 ^=%jR ^) 



In fig. 2, make the angle AOO equal to arc tan hB of 

 equation (2), and this determines the direction of the current 

 I 1>3 . Then upon the line so drawn take the point D so that 

 OD represents in length the number of units contained in 



,R 



