104 



EFFECT OF CAPACITY. 



For each set of readings construct a triangle of electro- 

 motive forces and deduce the angle of lead of the circuit by 

 measurement of the angle from the diagram. Calculate in 

 each case the power factor by dividing the energy voltage by 

 the total voltage. From the value of the power factor 

 ( = cos 0) find the value of </> from a table of cosines. 



Readings should be tabulated as follows : 



Determination of Phase Relations in Circuit with Capacity. 



Periodicity of circuit = 54. 



From results of this experiment the value of the 

 capacity can be calculated, as well as the value of the 

 resistance of the circuit. 



Thus the idle voltage F t = ~ ^, from which the value 



of K can be calculated*. 



Further, the energy voltage = F 2 = C R, from which the 

 value of R can be determined. 



The figures given in the table above are three sets of read- 

 ings taken from a series by way of illustration. The diagram 

 of voltage corresponding to these results is shown in Fig. 47. 

 In the case of the third set of readings, the value of the 

 capacity is given by the formula thus : 

 C 



K = 



47 



= -00002 farad. 



2^x54x69 

 = 20 microfarads. 

 Also the resistance of the circuit is given by 



JZ__?y -182 ohms. 



This resistance was actually a single 16 c.p. 100-volt 

 incandescent lamp. 



* This calculation can only be employed when the wave form of the current 

 is practically a sine curve. 



