240 Mr. Albert Griffiths : Some 



The current along BD varies as 



, f ,. & 3 YE sin e cos e . ± &* YE sin 2 e ^ ") , . - 



M &cos/>£+ — t sin^ 2 — _ cos pt J- —bigcospt 



C g k 3 YE sin 2 e 7 , fi ") 



cos ^l2 Tk h( *j + W~ " sin ^ 



2 



or 



g ^ 3 YE sin 2 e ? /c ") I ^3 YE sin e cos e _. 



= R cos (pt — a) say ; 

 R8= ||_* 3 YEBm* e _ 6@ |* + ^ 3 YEsiuecose| 



To make R, a minimum, 



where 



g jfcwYE sin 2 e 7/r > 2 f feYE sin ecos e^ 2 



From (4), 



,_ 1 _^ 3 YE_sin 2 € 

 ^~ 2 2k(g 



E it 



substituting 



g~" X + Y' 



x ^ 2 ^3 sin 2 e 

 °~ 2 U ' 



i ^sin 2 ^ 

 a — 2+4 ^ 



1 + i^3 s in 2 e 

 Apparent resistance = r-r . X . . . (8) 



l-i^sin 2 e 



If e is nearly equal to -x the result is very little influenced 

 by the frequency. 



If e= ? we have, noticing from (3) that 



k = fa + %hh> 



1 + 



K^Kin 



Apparent resistance = 77 . -& . . . (yj 



^"s 



^#1 4" #2% 



It has been already mentioned that experiments in which 

 a galvanometer and an intermittent ^contact caused by a 



