300 Prof. E. Edlund on Unipolar Induction. 



The induced current is therefore of equal intensity with the 

 two cylinders as with one only. 



Galvanometer- 

 deflections. 



scale-divisions. 



One cylinder on each side of the magnet,) qo.,v fop.7 

 at a distance of 8*5 centims. . . . J op. 



1011 



} 



One cylinder only, at 8*5 centims. from the) 00. n (00.0 



magnet 



f37-0) 

 1 38-0 y 

 (40-0 J 



The mean of these six observations is 37*5, consequently 

 nearly the same as before, though the distance from the 

 magnet has been almost doubled. 



A single cylinder at 3 centims. distance ) 07.5 f oq.a 

 from the magnet J oq.r i 



These observations, therefore, have verified the results of 

 the theory. 



It is unnecessary to say that the above deflections are cleared 

 of the feeble thermoelectric currents produced by the heating 

 of the points of contact during the rotation. It is easy to 

 eliminate these currents, seeing that they are independent of 

 the direction of the rotation. 



After this I proceeded to the following experiment : — 

 Two ebonite disks, agbli and ekfm (fig. 6), of equal dimen- 

 sions, their peripheries encased in a band of brass, were 

 pierced in the centre and passed over an axis cd, about which 

 they could be put in rotation, ab and ef represent two brass 

 rules fixed to the disks and communicating in a and e with 

 the brass bands, while they are insulated from them in b and 

 /and likewise from the axis cd. sn is a magnet passing- 

 through the two disks without any communication with the 

 two brass rules. One of the disks is placed at the height of the 

 south pole, and the other at the centre of the magnet, tu is 

 a brass bar communicating with the rules ab and ef; this bar 

 can be placed at different distances on both sides of the axis. 

 The brass springs p and q slide over the brass bands that en- 

 circle the disks, and thus communicate with the rules ab and 

 ef and the bar tu. These springs are connected with the elec- 

 trodes of the galvanometer. The rotation of the apparatus 

 about cd, in the direction indicated by the arrow, gives rise to 

 an electric current which passes from the spring q, through 

 the galvanometer, to the other spring. 



During the rotation the poles of the magnet describe circles 

 about the rotation-axis the radius of which is equal to r : 



