ELEMENTARY ELECTRICITY AND MAGNETISM. 25 



cuit passes through both portions, the portions are said to be 

 connected in series. When two portions of an electrical circuit 

 are so connected that the current in the circuit divides and a part 

 of it flows through each portion, the portions are said to be con- 

 nected in parallel. 



The ordinary arc lamps which are used to light city streets are 

 connected in series and the entire current delivered by the light- 

 ing generator flows through each lamp. On the other hand, if 

 the electromotive force of the generator is, say, 4,000 volts, and 

 if there are 80 similar lamps in series, the electromotive force 

 between the terminals of each lamp will be 50 volts. The elec- 

 tromotive force of a generator is subdivided among a number of 

 receiving devices connected in series. 



The ordinary glow lamps which are used for house lighting 

 are connected in parallel between copper mains which lead out 

 from the terminals of the generator, and, except for a slight loss 

 of electromotive force in the mains, the full electromotive force 

 of the generator acts upon each lamp. On the other hand, if the 

 generator delivers, say 1,000 amperes, and if there are 2,000 

 similar lamps connected between the mains, the current in each 

 lamp will be ^ ampere. The current delivered by a generator 

 is subdivided among a number of receiving devices connected in 

 parallel. 



Electric generators may be connected in series. When this 

 is done the electromotive force available for the maintenance of 

 current is equal to the sum of the electromotive forces of the in- 

 dividual generators. 



Electric generators which have equal electromotive forces may 

 be connected in parallel. When this is done the total current 

 delivered by the set is equal to the sum of the currents delivered 

 by the individual generators. 



Combinations of series and parallel connections are most fre- 

 quently used in grouping voltaic cells and storage batteries. 

 Series-connected-groups of cells may be arranged in parallel, as 

 shown in Fig. n, or parallel-connected-groups of cells may be 



