EFFECT OF CAPACITY. 



107 



Unlike the case of an inductive resistance with an iron 

 core, the capacity of the condenser, and consequently the 

 impedance of the circuit, will be the same for all values 

 of the current. 



Determination of Dependance of Current upon Capacity. 



Periodicity = 32 cycles per second. 



The voltage should be kept constant by means of an 

 additional variable resistance R t in the circuit or by regu- 

 lation of the generator voltage. For slight variations the 

 current readings may be corrected by increasing them in 

 the same ratio as any decrease in the voltage observed, 

 and vice versa. 



In this experiment, since the total current is small, care 

 must be taken not to introduce errors due to the volt- 

 meter current. If the voltmeter is not of the electrostatic 

 type, it should be connected so that its current does not 

 pass through the ammeter. 



Enter the readings in tabular form as shown, 

 and plot a curve for each set of readings, plotting capacity 

 horizontally and current vertically. 



Plot also a curve comparing impedance and capacity 

 with the same horizontal scale as before. 



The curves. given in Fig. 49 show the results obtained 

 with a subdivided condenser of 20 microfarads capacity, 

 three of the readings being shown on the table above. 

 The curves drawn as a continuous line show the readings 

 with the condenser alone in circuit. The dotted curves 

 show the results with a resistance of 4 ohms in series 

 with the condenser. Throughout the experiments the 

 voltage was maintained at 100, the frequency being 32. 



With low values of the capacity the current is very 

 small, and the resistance is practically without effect ; it 

 becomes relatively more important as the capacity and 



