378 

 and 



ELECTRICAL MEASUREMENTS 



C P 



If K z be depressed, still keeping KI closed, there will, in general, 

 be a deflection of the galvanometer, due to the difference in the 

 potentials of a and b. If there is a deflection, K\ and K 2 are 

 raised and the condensers completely discharged by the use of K z . 



After this another test is made with a 



r> 



different value of - 



By successive trials, adjusting either R M or R N , the deflection due 

 to the difference of potential of a and b at the instant of closing 

 KZ may be reduced to zero. When the adjustment is complete, 



Rff 



FIG. 223. -Connections for Gott method for comparing capacities. 



As anything which gives rise to a false distribution of potentials 

 in the network acbd will cause errors, all parts must be carefully 

 insulated, and K z especially, as it is handled. Leakage within 

 the battery or between the battery leads is not a source of error, 

 as it merely alters the P.D. applied to the network. Direct 

 leakage from the battery to the condenser circuits must be 

 avoided. Any leakage between the terminals of either condenser 

 is a source of error; this leakage may be through the dielectric 

 of the condenser or between the leads. If C x be imperfect in 

 this respect and K\ be kept depressed, the potential of b gradually 

 approaches that of c. The value found for C x will then be too 

 great and will increase with the time of charging. 



When cables are measured the core should be connected to 



