850 Mr. E. C. Snow on Pimm's Method 



R, the resistance of the battery. 



/?, the resistance of the galvanometer or telephone. 



L, the self -inductance of the coil. 



I/, the self-inductance of the galvanometer or telephone. 



E, the applied E.M.F., not necessarily constant. 



The resistances of the arms of the bridge are adjusted as 

 indicated. 



The following seven equations are derived immediately 

 from KirchhofFs laws applied to the various circuits : — 



a = C + cc . . . (1) b = V-x ... (2) 

 a = a f .+ x ... (3) I-a + b ... (4) 



BI + B& + *B&' = E (5) 



L^+ra+(A-r)a + p*+L'^-B6 = 0. . . (6) 



px + kBV-kAa' + U~=Q. ... (7) 

 at 



Also c = Qr Jt ( 8 ) 



From (1), (2), (3), (4), and (7) we find that 

 /> + A-BE dm 



a=z ' — ir^Pit' 



and 



, IcAE — c/m dm 



h q dt 



where 



f={p + kB + kA\{U + B + kB}-PB' 2 . 



gz=B,\p + kA+kB\+PAB. 



h=kA{R + B + kB}+kRB. 

 P h=U{R+B + kB}. 

 qh=Jj'R. 



Substituting these values of: a and & in (6) we have 



\x 



kB?> kBLdE 

 = __ ra+ _ E ____ . . (9) 



where 



M = L' + Ap 4- Bq—pr, 



and Jim = A/ -f Bg + ph. 



