88 CURRENT VALUE. 



Alternator armature. 



R Non-inductive resistance. 



r Resistance partly inductive. 



K Rotating contact maker. 



V Electrostatic voltmeter for reading instantaneous 



voltage. 



Fj Voltmeter for reading virtual voltage of alternator. 



VS Throw-over switch. 



C Condenser in parallel with electrostatic voltmeter. 



Instructions. Connect in series to the terminals of the 

 generator a non-inductive resistance and the inductive 

 resistances which are to form the circuit. Connect to the 

 centre terminal of a throw-over switch an electrostatic 

 voltmeter in series with the rotating contact maker. 



Connect the other pole of the voltmeter to the terminal 

 of the non-inductive resistance which is supplied direct from 

 the alternator. 



To one side of the 2- way switch connect one terminal of 

 the generator ; to the other side connect the terminal of the 

 non-inductive resistance nearest to the same generator 

 terminal. Connect a voltmeter to the terminals of the 

 generator. If found necessary, connect a condenser in 

 parallel with the electrostatic voltmeter. A battery may be 

 used in series with the electrostatic voltmeter as described in 

 the previous experiment, if necessary to read the low 

 voltages. 



For each position of the contact maker read the instan- 

 taneous voltage of the alternator, and the instantaneous 

 voltage of the non-inductive resistance by putting the switch 

 first to one side and then to the other. Throughout the 

 experiment maintain the voltage of the alternator constant 

 by regulating the field if necessary. Results should be 

 entered in tabular form, and curves of current and 

 voltage should be plotted on the same sheet of squared paper. 

 The resulting curves will be similar to those shown in Fig. 7 

 if the alternator gives a true sine curve. Usually this will 

 not be exactly the case, and the curve may more nearly 

 resemble some of the less simple curves given later. Whatever 

 be the shape of the curve, the angle of lag between current 

 and voltage should be measured as the angle (plotted 

 horizontally on the curve) between the points at which the 

 curves of current and voltage cross the zero line. 



