H. A. Rowland — Electrical Measurement. 441 



Method 15. 



1 ^ or FI^L" or 



b*V,C" ' C" 



R'R^R, + R,„) (R" + R") -R'^R "R,,, 

 R'R„-R'"R„, 



V or ^ or - 5*L C" - A^V^UVR J 

 c or L „or ol^ ~R'R (R" + R'')_R'R R" 



When R /y/ = oo we have 



L R'R (R" + R"') — R"R ; R '" __ -p, p R" 

 <F = — R 777 = KU /,-|pL K K /~ KK //J 



£ 2 L 0" - E 



R"R" 



If we adjust by continuous current, we shall have R /// R / — 

 R'R,, = 0. For a condenser we can make R" = provided 

 there is no electric absorption. In this case Ifhfi" is indeter- 

 minate and we can adjust to find -^,. However, two simulta- 



neous adjustments are required. 



But I have shown that the presence of electric absorption 

 in a condenser causes the same effect as a resistance in its cir- 

 cuit, the resistance, however, varying with the period of the 

 current. Hence R" must include this resistance. However, 

 the value of R" will not affect the first adjustment much and 

 so the method is easy to work. If it is sensitive enough it 

 will be useful in measuring the electric absorption of conden- 

 sers in terms of resistance. 



It has the advantage of being practically independent of the 



current period for — as it should be. 

 \j 



For comparison of capacities the same simplification does 

 not occur. 



Indeed the method is of very little value in this case, being 

 surpassed by 16. 



Method '16. 

 (A) [R / R"-R // R'] [W + r'+r"] + W[R/'-r'RJ = 



L' C, R" CWr") 



or 7=f = -j- + 



L, C R„ ' R„(W + r'+r") 



The first equation is satisfied by adjusting the Wheatstone 

 bridge so as to make 



(R,R"-R„,R') = R/'-R y / = o R / (R // +r ,/ )-R // (R , + r') = 



