240 VOLTAIC ELECTRICITY. 



current has the same direction in all, constitutes a 

 Voltaic battery. The usual method is to connect the 

 positive plate of one element with the negative plate of the 

 next, as shown in Fig. 183. When thus connected, they 

 are said to be coupled "in series." Sometimes all of the 

 positive plates are connected by a wire, and all of the neg- 

 ative plates by another wire. The cells are then said to be 

 joined "in multiple arc." (See Fig. 184.) 



38O. Batteries of High and of Low Re- 

 sistance. Each kind of Galvanic cell has an internal 



FIG. 183. 



resistance, depending upon the liquid used, the distance 

 between the plates, and the size of the plates. The resist- 

 ance of the liquid conductor is several million times as 

 great as that of a similar metal conductor. The distance 

 between the plates determines the length of the liquid 

 conductor ( 378), and the size of the plates, its area of 

 cross-section. A battery of cells joined in series is called 

 a "battery of high resistance." A battery of cells joined 

 in multiple arc is called a " battery of low resistance." For 

 a long circuit of great external resistance, a battery of high 

 resistance is needed. For a short circuit of small external 



