PRINCIPLES OF ALTERNATING CURRENT 



205 



the component AE is 90 out of phase with the current. 

 In (6) the current is resolved into two components, OA 

 in phase with the voltage OE, and AI at 90 with the 

 voltage. The component OA is called the " watt com- 

 ponent " or " power component/' or " in-phase component " 

 in various books. The component AI (or AE) is called the 

 " wattless component " or " quadrature component " or 

 " out-of-phase component." 



All of these terms are more or less vague and ambiguous. 

 We shall use the words active and reactive to designate the 

 two components. That component of the voltage in 

 phase with the current we shall call the active component 



(a) 



I 



(&) 



FIG. 124. Vector Diagrams Showing Active and Reactive Components 

 of Voltage and Current. 



of the voltage or merely active voltage. The component 

 of voltage 90 out of phase with the current we shall call 

 the reactive component of the voltage or reactive voltage. 



Similarly the component of current in phase with the 

 voltage will be called the active current and the component 

 of current at 90 with the voltage will be called the reactive 

 current. 



The product of the voltage and active current (or current 

 and active voltage) gives the active power of the circuit. 



The product of the voltage and reactive current (or current 

 and reactive voltage) gives the reactive power of the circuit. 



When the single term power is used in connection with 

 an a-c. circuit active power , or true power is always signified, 



