612 



LENZ OK ELECTRO-MAGNETISM. 



metal could be perceived except at the ends which served for con- 

 necting them. 



I now proceed to the experiments themselves. 



I. On the Influence of the number of Convolutions upon the Electro- 

 motive Power produced in them. 

 In these experiments I connected the wire No. 3 with the multiplier 

 so that the conducting wire and the electromotive spirals were formed 

 of one and the same piece ; the length of this wire was about fifty feet: 

 here however this is of no consequence, as it remained the same in all 

 the experiments. The experiments themselves are contained in the 

 following table. 



From this series of experiments we must now deduce the electromo- 

 tive power of the spirals for each number of convolutions, for which 

 purpose the following considerations will be of service. 



The action of the electric current in the wire of the multiplier upon 

 the magnet needle, is a momentary one, since the current itself exists 

 only for a moment ; we may therefore consider this action as an im- 

 pulse given to the needle, and shall be able to measure its force by the 

 velocity which it imparts. But the velocity of the needle at its exit is 

 evidently as great as that which it acquires when it springs back to the 

 point of exit ; it may therefore be expressed (/ being constant) by 



A = y v' (sin. vers, a) 

 where A represents the sought for velocity of the exit ; or according 

 to what has been above stated, the magnitude of the current in the 

 wire of the multiplier, and a the angle of deviation of the needle pro- 

 duced by this force. This expression changes however by the sub- 

 stitution of 2 sin.'- \a, instead of sin. ver.s. a into the following 



A = p • sill. Jj a 

 if we put p '= f -^f 2. 



