Intelligence and Miscellaneous Articles, 77 



the resistance 6, and therefore the heat will increase in the condenser 

 and in the soft iron ; for this is the effect of this extra current. 



Inducing Current. — It is clear that the inducing current transfers 

 the heat into the induced wire, the condenser, and the iron. We are 

 utterly ignorant of the manner in which this transfer is accomplished. 

 It might be that the inducing current preserved its intensity, and 

 lost some of its heat by radiation. But this is not the case : Ohm's 

 formula ceases to be applicable ; the current loses force ; it preserves 

 the heat which corresponds to its reduced intensity I (that is to say, 

 a heat equal to the product of I 2 into the resistance r) ; but it has 

 transmitted around it, by a mechanism with which we are unac- 

 quainted, and distributed according to the laws which we have just 

 established, the heat corresponding to its lost intensity. 



Now, in proportion as 6 increases, the heat increases in the con- 

 denser and in the soft iron ; it decreases in the coil (3 ; it first in- 

 creases and then diminishes in the resistance 6. All this heat is un- 

 doubtedly taken from the sum of the thermal units yielded by the 

 pile ; what is left disposable is found in the inductor, which must thus 

 vary according to complicated laws. All that can be said and that 

 is justified by experiment is, that the intensity of the inducing current 

 diminishes as 6 increases, and that it attains a minimum for 6=oo . 



Broken Currents. — The succession of these phenomena leads us 

 little by little to the case in which 0= oo — that is, to the moment when 

 the induced coil is open, when it gives no more heat, when it has 

 nothing but tensions which are alternately contrary, in which case 

 nothing is expended. This coil may then be neglected or suppressed ; 

 everything is reduced to the inducing circuit, to the condenser, and 

 to the soft iron. It is the problem of the broken currents, which 

 continues that of the induction, with which it forms a concordant 

 whole. 



1 . When 6 increases to infinity, the intensity of the inducing cur- 

 rent diminishes to a minimum. If now the resistance of the coil b 

 be augmented by an increasing quantity t, this intensity will continue 

 to decrease according to a very simple law, that of Ohm, 



t nAa, 



A and R being generally greater than the electromotive force and 

 the resistance of the n elements of the pile used. 



2. The quantities of heat C and C developed by the current in the 

 resistance t and in the coil b are in conformity with Joule's law 

 extended to broken currents, 



c=fL 2 , c -= b Z 



a a 



3. The soft iron has developed a quantity of heat increasing with 

 to a fixed limit ; this heat now decreases progressively and ac- 

 cording to Joule's law, as if the soft iron were a wire having the 

 resistance/: 



c"=/! J . 



