Prof. E. Edlund on Unipolar Induction. 301 



their velocity may therefore be denoted bj r Q v, if v is the 

 angular velocity. The velocity of the bar tu is rjo } i\ de- 

 noting its distance from the rotation-axis. The relative velo- 

 city of the bar with respect to the magnet regarded as im- 

 movable will therefore be (r + r-^v, as already remarked above. 

 If the bar passes through the points x and y on the same side 

 of the axis of the rotation as the magnet is placed, and at the 

 distance r x from that axis, the relative velocity of the bar with 

 respect to the magnet will be (r -—r^)v. Thus the relative 

 velocity of the bar will in both cases be the same as if the 

 magnet were regarded as immovable, and the disks as well as 

 the bar as in rotation about it with the same angular velocity 

 as that which they have in reality about the axis cd. It is 

 the same with the brass rules ab and ef. 



This being admitted, let us suppose we make two experi- 

 ments with the same velocity of rotation, but with this dif- 

 ference — that in the one the bar occupies the place indicated 

 by the figure, while in the other it is placed in xy. In both 

 cases the induction will be the same as if the apparatus were 

 in rotation about the magnet at rest. In the first case we 

 have to consider the induction in the circuit atue as well as in 

 the two rings surrounding the disks, and in the second case 

 the induction in axye as well as in the same rings. Now the 

 calculation given above has shown that the induction in the 

 circuit atue is equal to that of the circuit axye. Therefore, if 

 these deductions are correct, the intensity of the induced 

 current must be the same, whatever the situation of the bar. 



The experiments gave the following deflections, in divisions 

 of the scale : — 



The bar placed on the oppposite The bar on the same side of the 

 side of the axis to the magnet. axis as the magnet. 



r x =40 millhns. r 1 = 24 millims. r x = 2-4 millims. r x = 40 millims. 

 17-0 17-0 15-5 16-0 



16-0 16-0 17-2 17-3 



16-2 15-2 17-0 16-0 



Mean 16*4 16*1 16*6 16*4 



As the numbers can be regarded as equal, it follows, as cal- 

 culation also shows, that the intensity of the current is inde- 

 pendent of the position of the bar. 



According to the preceding statement, unipolar induction 

 ought not to be considered a real induction, but an ordinary 

 electrodynamic phenomenon due to the action of the magnet 

 upon the electric currents produced by the motion of the 

 conductor relatively to it. As for the action of the magnet, 

 whether the currents on which it acts are produced by spe- 



