DIRECT CAPACITY MEASUREMENT 



21 



Additive Property of Direct Capacities 



Connecting a capacity between two terminals adds that capacity 

 to the direct capacity between these terminals, and leaves all other 

 direct capacities unchanged. Connecting the terminals of two distinct 

 electrical systems, in pairs, gives a system in which each direct capacity 

 is the sum of the corresponding two direct capacities in the individual 

 systems. Joining two terminals of a single electrical system to form 

 a single terminal adds together the two direct capacities from the two 

 merged terminals to any third terminal, and leaves all other direct 

 capacities unchanged, with the exception of the direct capacity 

 between the two merged terminals, which becomes a short circuit. 

 Combining the terminals into any number of merged groups leaves 

 the total direct capacity between any pair of groups unchanged, and 

 short-circuits all direct capacities within each group. 



These several statements of the additive property of direct capaci- 

 ties show the simple manner in which direct capacities are altered 

 under some of the most important external operations which can be 

 made with an electrical network, and explain, in part, the preeminent 

 convenience of direct capacity networks. 



Fig. 2 — Colpitts Substitution Bridge Method for Direct Capacity 



Since the additive property of direct capacities is sufficient for 

 explaining the different methods of measuring direct capacities we 

 may now, without further general discussion of direct capacities, pro- 

 ceed to the description of the more important methods of measurement. 



