48 Dr. A. Stoletow on the Magnetizing -Function of 



11*75), the following equations became valid : — 

 E 



^mon'-r n . R=32 . 626 . 



19-172 

 Before passing to the proper measurements, I will give an ac- 

 count of two preliminary experiments, which I made for the 

 purpose of ascertaining the regular course of the phenomenon 

 and to test its accordance with theory. 



If we leave the magnetizing current i unchanged, from equa- 

 tion (1) it follows : — 1, that the induced electromotive force 

 increases proportionally with the number of the secondary turns ; 

 2, that it depends only on the number, and not on the quality, 

 of the turns. 



Lenz found similar laws by experiment when investigating the 

 induced currents excited in a spiral wire enclosing an iron cy- 

 linder as soon as the cylinder was pulled away from the pole of 

 a powerful steel magnet*. Theoretically, however, these laws 

 can only be derived under the assumption that the cylinder is 

 infinitely thin and longf. 



I conducted the current of a DanielPs series through the pri- 

 mary wire of the ring. Divisions 100, 150, 200, and 250 of 

 the secondary wire were connected with each other and with a 

 galvanometer of great deadening force. The connexion was 

 made in various ways, so that the numbers of effective turns were 

 respectively 100, 200, 300, 400, 500, and 700. As the resist- 

 ance of the secondary circuit remained unaltered, the deflections 

 observed on the galvanometer when the primary current was re- 

 versed were proportional to the induced electromotive forces. 

 The mean numbers of these deflections, each from eight obser- 

 vations, were : — 

 with 100 turns, 200, 300, 400, 500, 700, 



= 47-2 scale-divisions; 94*4; 1404; 189; 236'4; 329'9. 



Starting from the number 329*9, the others are found by cal- 

 culation to be 



47-13, 94-26, 141-4, 1885, 2356. 



When the divisions were so combined that the number of 

 turns running in one direction was equal to the number in the 

 opposite direction, I obtained on the reversal of the current the 

 small deflections ±1*5, which are probably to be attributed to 

 the imperfect homogeneousness of the iron mass or of the pri- 

 mary turns J. When 150—100 — 50 turns were employed, the 

 magnet remained perfectly at rest. 



* Wiedemann, Galvanismus, vol. ii. p. 634. 



t Kirchhoff, Crelle's Journal, vol. xlviii. p. 368. 



X According to theory, the action of the ring upon external magnets 



