442 H. A. Rowland — Electrical Measurement. 



That is 



R^ _5l_!1 



U u ~ R" T. r" 



We can then adjust W with alternating currents. This is a 

 very good method and easy of application but requires many 

 resistances of known ratio. Many of these, however, may be 

 equal without disadvantage. A well known case is given by 

 making r' and r" = 0. 



(B) By placing self inductions or condensers in R, and r ff 

 instead of the above we have the following 



c" 72T „ L, RXW + R")-^'^ 



C ' l" "R"(W+r' + r")Wr" 



or -4, or - 6 2 L,1" = 



VC t c" c' 



(W" + r' + r ") (R / R // -R // R / ) + W(R /-R / / / ) 



W+R" 

 Making R" = we have 



c" ;2T „ L, R/W-R'R,, 



~ bW> ° r W - -VW» = R'R ll + r'R„ (i+ I)- £ 

 (B,W-B'B„) 



In case we adjust the bridge to R,W — ~R'R lt = and a con- 

 denser is in r" so that we can make r" — 0, the value of 



— WL t G n will be indeterminate and we can find -j t by the adjust- 

 ment of "W alone. 



This is an excellent method, apparently, as only one adjust- 

 ment is required. 



However, -see the remarks on method 15. This present 



method r"=0 for — is Anderson's with, however, alternating 



currents instead of direct as in his. 



The other two values are imaginary in this case. Indeed 



the whole method, B, is only of special value for -, as two 



c 



adjustments are needed for the others. 



Method 17. 

 (A ) W = oo . R = oo 



& 2 ML' = R / R"-R // R' 



L^ _ R' + R,-{-R" + R„ 

 M~~ R, 



