320 Steady Currents in Linear Conductors [OH. ix 



We can now express in symmetrical form the relations which have been 

 obtained in 360 to 362, as follows : 



I. ( 362). The conductors 1, 2 and P, Q will be conjugate if 



= p. 

 dK l>P dK 2tQ 



II. (Equation 293). // the conductors 1, 2 and P, Q are not conjugate, 

 a current X entering at P and leaving at Q produces in 1, 2 a fall of 

 potential given by 



d JjT lt 



III. (Equation 295). If the conductors 1, 2 and P, Q are not conjugate, 

 a battery of electromotive force E placed in the arm PQ produces in I, 2 a 

 fall of potential given by 



and a current from 1 to 2 given by 



^ 



dK 



All these results and formulae obtain illustration in the results already 

 obtained for the Wheatstone's Bridge in 351 and 352. 



SLOWLY- VARYING CURRENTS. 



365. All the analysis of the present chapter has proceeded upon the 

 assumption that the currents are absolutely steady, shewing no variation 

 with the time. Changes in the strength of electric currents are in general 

 accompanied by a series of phenomena, which may be spoken of as " in- 

 duction phenomena/' of which the discussion is beyond the scope of the 

 present chapter. If, however, the rate of change of the strength of the 

 currents is very small, the importance of the induction phenomena also 

 becomes very small, so that if the variation of the currents is slow, the 

 analysis of the present chapter will give a close approximation to the truth. 

 This method of dealing with slowly-varying currents will be illustrated by 

 two examples. 



