73 INDUSTRIAL APPLICATIONS. 



by electricity or in transmitting force at a distance. This is the 

 problem of the distribution of energy. 



The simplest arrangement consists in putting all the apparatus in 

 series in the circuit, by which any given fraction can be utilised in 

 each. This has the twofold inconvenience that recourse must be had 

 to very high electromotive forces, which may be dangerous, and give 

 rise to important losses from defective insulation, and also that a 

 break of the current in any one part stops the work in all the rest. 



The apparatus should be so arranged that a break of the work 

 in any one part does not hinder the general work, and as much as 

 possible that a modification in the useful work does not alter the 

 working. The problem is the same as that of the regulation of 

 steam-engines; no exact solution is possible. 



In incandescent lighting the lamps are usually arranged in 

 parallel series with two conductors of large section in connection 

 with the machine. Let A and B (Fig. 261) be the two poles of 

 the machine; AAj and BB X the principal conductors; A^, A 2 B 2 



A, 



Fig. 261. 



...A n B n the points where the useful resistances x lt x 2 ,...x 3 are 

 connected; a lt a 2 ...a n the resistances of the principal conductors 

 comprised between two successive contacts that is to say, the re- 

 sistances of the portions of the circuit AjA 2 + B^, A 2 A 3 + B 2 B 3 , . . . 

 A n A + B n B; y lt y<^...y n , the total resistances between the corre- 

 sponding points A 2 B 2 , A 3 B 3 , A n B n AB, not counting the branch 

 directly between them. We have 



__ I __ 



x n A-l 



