INDUCTANCE AND CAPACITY 397 



no relation to the dielectric or insulation resistance given by 

 measurements with steady currents. The latter may be many 

 thousand times the equivalent dielectric resistance as determined 

 by alternating currents. 



Fleming and Dyke in their researches on the power factor and 

 equivalent conductivity of dielectrics 18 used a bridge in which 

 the arms M and N were formed by two perfect (air) condensers. 

 The arm P contained a perfect (air) condenser in series with a 

 non-inductive resistance. As high frequencies were used (up 

 to 6,000 cycles per second), it was necessary to use a telephone 

 detector. 



7 C 



With this bridge J^ = -*-; therefore, referring to the previous 

 6 N L M 



demonstration, 



_ 



~ C 

 and 



c -C*( _ CP. _ \ 

 " C*U + r> 2 Cp 2 <o 2 /' 



The tangent of the power-factor angle of the condenser under 

 investigation is given by 



tan 6 X = - 



When air condensers are used in the bridge arms they must be 

 properly screened or else placed so far apart and so far from the 

 observer that difficulties due to electrostatic induction are 

 avoided. All the connections should be of very fine wire. 



Bridge for Measurement of Electrolytic Conductivity. The 

 impedance bridge, arranged as in Fig. 231, is employed in the 

 measurement of the conductivities of electrolytes. 



On account of the capacity action in the electrolytic cell it is 

 necessary to use an adjustable air condenser in parallel with the 

 resistance in the arm P. When the bridge is balanced 



p R M P 

 KX jj-~ ftp' 



Wagner Earth Connection. When a telephone is used as a 

 detector in these bridge methods, difficulties are encountered 

 due to a difference of potential between the observer and the 



