EFFECT OF CAPACITY. 



109 



EXPERIMENT XIX. DETERMINATION OF DEPENDENCE 

 OF CHARGING CURRENT UPON FREQUENCY. 



DIAGRAM OF CONNECTIONS. 



Ml 



FIG. 50. 



ML M z Source of alternating current. 

 C Condenser. 

 V Voltmeter. 

 A Ammeter. 

 R Adjustable resistance for keeping voltage across 



condenser constant, if this cannot be done 



by other means. 

 8 Switch for breaking circuit. 



Instructions. Connect in series a condenser and ammeter 

 and switch. Connect these to a supply of alternating 

 current of variable frequency. Unless this supply can be 

 maintained at a constant voltage, a regulating resistance 

 must be put in the circuit, so that the voltage across the 

 condenser may be maintained at a constant value. 

 Connect a voltmeter across the condenser. If this volt- 

 meter is not of the electrostatic type it must be connected 

 across the ammeter also, so as to prevent the ammeter 

 reading the voltmeter current, or must be disconnected 

 when the current readings are being taken. 



For a range of different frequencies of current, adjust 

 the condenser voltage to a constant value, and observe 

 the frequency and current. The frequency will usually 

 have to be determined by a speed counter applied to the 

 alternator supplying the circuit, the frequency being 

 given by 



^ n x p n = revs, per min. 



Frequency = 



60 



p = No. of pairs of poles. 



