224 ELECTRICAL MACHINERY 



It may be seen from Fig. 134 that tan <i> = EB/OB or 



tan<j> = - ....... (57) 



R 

 or 



cos - 



The term R 2 +2^fL--\ is called the impedance 



of the circuit and the term f 2xL - is called the 



f 2x/L ^-^ 



reactance of the circuit. The letter Z is used for impe- 

 dance and the letter X for reactance. Equation (56) 

 would then be written, 



\/R 2 +X 2 

 and 



(59) 



cos<l> = ^; (60) 



or 



tancl> = ! (61) 



From these formulas any series circuit can be calculated. 

 In case the circuit contains only capacity and resistance 

 the current would be obtained by using equation 56 and 

 putting L = 0. If there is neither inductance nor capacity 

 in the circuit, equation 56 reduces to the well known Ohm's 

 law / = . 



