204 



vanometer. G. Suppose the magnet to be revolved at a high speed. Few 

 lines of force cut y\-\ as it is parallel with the axis of the magnet. W 

 is cut by the lines passing from pole to pole and if the pole strength is 

 suliiciently great and the magnet is revolved rapidly, the galvanometer 

 will indicate a current— and therefore an induced e. m. f. If w and w^ 

 are led from the magnet as in Fig 2, it is evident that the resultant e. 

 m. f. generated is zero, since that generated in w opposes that generated 

 in w\ But suppose that w is of one metal and w"^ of another, if the 

 e. m. f. generated in each is not the same, the galvanometer, if sutttciently 

 sensitive, will indicate a current. The wire w' may be replaced with a 

 tube containing an electrolyte and the electromagnetic induction in the 

 electrolyte measured. To increase the sensitiveness of the apparatus 

 there may be a number of w"s and w''s connected as shown in Fig. 3. 







M 



\N 







t 



a 



#c 



M 





Fig. 3. 



