220 



ELECTRICAL MACHINERY 



= 0. However, actual condensers do use some power 

 because of the heat losses in the dielectric and plates. 

 These losses are small, being practically zero in mica con- 

 densers and somewhat larger in paraffine condensers. The 

 angle of lead in different condensers varies from about 86 

 to a few minutes less than 90. 



Capacity Reaction. The unit of capacity is the farad. 

 If C is the capacity of a condenser in farads and the voltage 



Rate of Change 

 of Voltage 



FIG. 131. Curve Diagram of Condenser Reaction. 



(virtual) impressed on the condenser is E, the frequency 

 being/, then 



/(virtual amperes) =2x/C#. . . . (51) 



Writing this equation in another form we have, 



1 



(52) 



Now E is the impressed force on the circuit and therefore 



must be the reaction of the circuit. In Fig. 132 is 

 zx/C 



shown the current I leading the impressed force E by 90; 



