120 EFFECT OF CAPACITY. 



In each case the power == current x energy com- 

 ponent" of voltage. Thus the power in the inductive 

 portion r is the product of the current, and the energy 

 component of AB, i.e., AC. 



Power == W r == G x AC. 



= -78 x 41-7 == 32-5 watts. 



Similarly in the total circuit, the energy component is 

 represented by the line 0(7, and the power 



= w t ==c* oc. 



= -78 x 86-7 == 67-63 watts. 

 In the non-inductive resistance R the power 

 = W R == G x OA. 



= -78 x 45 == 35-1 watts. 



In the condenser the power is zero, since* the voltage 

 is entirely idle voltage period behind the current.* 



Evidently the power in the circuit could be calculated 

 directly from the voltmeter readings, in the same way as in 

 Experiment XIII. 



The triangle OAD would in this case be the triangle 

 whose sides would represent the voltages to be employed 

 in the calculation. Another and more direct way would 

 be to calculate the power from the triangle OAB obtained 

 from the inductive and non-inductive portions of the cir- 

 cuit, and omit the consideration of the voltage across the 

 condenser. Obviously this might not be possible if the 

 capacity were not confined to one pVrtion of the circuit. 



Resonance. The conditions just alluded to may give rise 

 to what is called " Electric Resonance." It has been shown 

 in the preceding discussion that when special relations 

 exist between the capacity K, the self-induction L, and the 

 frequency in a circuit, the voltage at the terminals of the 

 self-induction and capacity connected in series, may be 

 less than the voltage at the terminals of one of them. 

 Thus, if the voltage of an alternator be connected to a 

 circuit containing a condenser and choking coil, it 

 is possible that the voltage at the terminals of the 

 condenser or choking coil might be greater than 

 the voltage supplied by the alternator. An example 

 will serve to illustrate this. 



* The small losses due to resistance and dielectric hysteresis in the con- 

 denser are neglected as being too small to affect the results. 



