4 -A] SERIES AND PARALLEL CIRCUITS. "3 



will be the same as readings obtained simultaneously with three 

 ammeters and three wattmeters. 



34. Repeat at a second frequency. 



35. (e) Measurement of Resistance. Measure the resist- 

 ances R! and R 2 by direct current, 17, Exp. i-A. 



PART HL RESULTS. 



36. In each test, (a), (&), (c), and (d), select say two sets 

 of readings at each frequency and construct vector diagrams 

 showing the magnitude and relative phase positions of the various 

 currents and voltages. Compute for the various circuits, and 

 parts of circuits, the power factor and the phase difference 

 between current and voltage. The prime object is to obtain a 

 clear understanding of the relations between the various quanti- 

 ties, rather than to obtain exact numerical values. 



Adjusting 



FIG. 4. FIG. 5. 



Circuit containing resistance J? x . 



37. (a) Resistance Alone. For this case, the current and 

 electromotive force are in phase, and true power is equal to 

 the product, volts X amperes. Power factor W-t-EI=i; 

 cos0=i; = o. See Fig. 5. 



38. (b) Coil Alone. The current I lags behind the electro- 

 motive force E by an angle 0, as in Fig. 7. The true power W, 

 indicated by the wattmeter, is less than the volt-amperes or 

 apparent power, El ; thus 



9 



