ELECTRIC CIRCUITS 



83 



e.m.f. e of the battery between C and D. RI and Rz are resist- 

 ances connected in the circuit. 



The electromotive force acting in the direction of the current 

 is E e and is consumed in driving the current I through the 

 two resistances RI and R 2 and by Ohm's law. 



77* - 77? I 77? 



-j \j -Z -iLl "T~ J- -^^2* 



If IRi and IR 2 are considered as e.m.f. 's opposing the current, 



I. R 2 

 FIG. 65. Kirchoff's second law. 



then the sum of all the e.m.f. 's around the closed circuit A BCD is 

 E - e - IR l - IR 2 = 0. 



The second law is illustrated by the circuit A BCD in Fig. 65. 

 The current I divides at B into two parts /i and 7 2 ; I is numeri- 



R 2 



cally equal to the sum of I\ and h, and therefore the sum of all 

 currents flowing toward the distributing point B is 



I - (Ii + / 2 ) = 0. 



61. Resistances in Series. If a voltage E is applied across 

 a circuit consisting of a number of resistances RI, R z and R% con- 

 nected in series (Fig. 66) the total resistance of the circuit will 

 be equal to the sum of the resistances of the different parts. 



