DETERMINATION OF WAVE FORM 615 



The magnitude of tbe deflections may be controlled by means 

 of the battery and the resistance ba. 



The electrometer is calibrated by use of direct-current voltages 

 as indicated. 



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a Are 



Fi. 379. Wave form determined by euutaet method. 



The electrometer readings, reduced to volts, are plotted against 

 the readings on the uniformly graduated arc, as shown in Fig. 379, 

 and a smooth curve drawn through the points, 



If an electrostatic voltmeter is used in place of the el" 

 meter, a difficulty is encountered, since the deflections depend 

 on the square of the voltage; hence those obtained near the zero 



T& *.fc-0 



^tfl f 

 gt 



pointe of the wave will be very small This diflkulty m* 

 obviated by working from a abe zero, A battery of soft 

 roltsge to give a large deflaetion is joined in serw*witbtb* 

 meter; thus when reading are taken the voltage to be measured 



