INDUCTANCE AND CAPACITY 



401 



may be tried and so on. Lastly, a final attempt to obtain a 

 perfect zero indication of T may be made by altering R and L P 

 slightly. 



A simple form of impedance bridge adapted to the determina- 

 tion of inductances in terms of capacities and vice versa is shown 

 diagrammatically in Fig. 234. 



Equal ratio arms are employed; they are advantageous in any 

 bridge arrangement since their equality may be checked at any 

 time by simply reversing them. 



FIG. 234. Diagram of impedance bridge for comparing an inductance with 



a capacity. 



The arms M and N are equal and they as well as r x and R P 

 are non-reactive, so when the bridge is adjusted the arm X is, 

 in effect, non-inductive, the inductance and capacity being 

 balanced. Then 



fi, = fix + tx + 



If L x is to be determined in terms of a capacity having no 

 appreciable losses, the balance is obtained by adjusting R P and 

 r x . From equation (3 la), 



L x = 



C r* 



XX 



2 r 2 

 X 1 X 



=Rp 



(32) 



(33) 



If the equivalent capacity and insulation resistance (C x and 

 r x ) of an imperfect condenser are to be determined, an adjustable 



26 



