EFFECT OF CAPACITY. 119 



radius equal to V l from A as centre, and a second circle 

 about of radius V v the resultant voltage across both 

 inductive and non-inductive resistances. The intersection 

 of these circles will give the point B, and AB represents 

 in phase and magnitude the voltage V r 



The triangle GAB is exactly similar to the triangle 

 obtained in Experiment XIII. in a circuit with induc- 

 tance and resistance only. The total energy voltage of 

 the circuit is obtained by drawing a vertical line BC to 

 meet OA produced in C. Then 00 is the energy com- 

 ponent of the total voltage of the circuit. The line CB 

 represents the idle voltage due to self-induction 



The condenser voltage will be in phase with BC, but 

 opposite in direction, or, more accurately, it will be 180 

 out of phase with BC. 



Hence the condenser voltage V 3 is represented by the 

 vertical line BD measured from B upwards. Finally, the 

 total voltage of the circuit is represented in phase and 

 magnitude by the line OD, which in the case for which 

 Fig. 56 is drawn is seen to be later than the current in 



O 



phase, so that there is a leading current in the circuit. 

 The line BC represents the portion of the condenser volt- 

 age which is neutralised by the idle voltage of self-induc- 

 tion of r. Thus, if the circuit had been non-inductive, 

 the resultant voltage of the circuit would have been the 

 dotted line OD 1 , where CD 1 is equal to the condenser volt- 

 age V 5 or BD. It i thus seen that the voltage required 

 to send a given current may be reduced by the presence of 

 both inductance and capacity. If the inductance had been 

 greater, so that CB = BD, the self-induction and capacity 

 would exactly have neutralised each other, and the voltage 

 of the circuit would only be of the magnitude necessary 

 to send the given current through a non-inductive resis- 

 tance. 



The diagram shown in Fig. 56 is drawn for the first 

 set of readings given on the table above. It would form 

 an excellent exercise for the student to draw diagrams for 

 the remaining readings, if he has not the opportunity of 

 carrying out a set of readings for himself. 



Determination of Power from the Diagram. Having drawn 

 this diagram, it is an easy matter to calculate the power 

 in each part of the circuit from it. 



