204 



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

 lines of force cut w\ as it is parallel with the axis of the magnet. AY 

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

 sufficiently great and the maguet is revolved rapidly, the gah'anometer 

 will indicate a current — and therefore an indticed 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\ Btit 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 stifflciently 

 sensitive. Avill 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 



W 



W= 



l/V' 



®s 



M 



M 





Fig. 3. 



