THE TRANSFORMER. 



135 



EXPERIMENT XXIII. DETERMINATION OF DROP IN 

 TRANSFORMER. (DIRECT READING METHOD.) 



DIAGRAM OF CONNECTIONS. 



FIG. 62. 



M lt M 2 Source of alternating current. 

 /., //. Primary and secondary windings of trans- 

 formers A and B. 

 R Variable non-inductive resistance for altering 



load of transformer A . 

 A Ammeter for reading output of A. 

 V Voltmeter for reading drop of transformer A. 

 $! Switch for breaking load circuit. 

 $ 2 Switch for connecting transformers to supply. 

 Instructions. Connect* both transformers to the source 

 of supply through a switch, primary or secondary windings 

 being chosen according to the voltage available. 



Connect the free windings of the two transformers together 

 in opposition, inserting a low-reading voltmeter in the circuit. 

 Connect one of these windings also to a load circuit com- 

 prising a variable resistance, ammeter, and switch. 



Before putting the low-reading voltmeter in the circuit, 

 it is necessary to make sure that the windings connected to 

 it are in opposition and not in series. If they are in series, 

 the voltmeter will get double the voltage of a single trans- 

 former. First, therefore, put in place of the voltmeter a 

 set of lamps in series or a high-reading voltmeter, or a thin 

 piece of fuse wire, according to voltage to be expected. Close 

 switch $2, and note if there is considerable voltage. If 

 so, interchange the connections of one transformer. 



* The advantage of making the connection of both transformers to the 

 supply by a single switch is that the voltmeter does not receive a high 

 voltage, as might be the case if one transformer were connected to the supply 

 before the other. 



