EXPERIMENT IN MAGNETO-ELECTRIC INDUCTION. 



123 



Let Msmd be the value of the potential of the magnets on the coil of 

 the armature ; then if the armature revolves with the angular velocity n, the 

 electromotive force due to the machine is Mncosnt. 



Let R be the resistance of the wire which forms the coil of the armature 

 M and that of the fixed electromagnet. 



Let L be the coefficient of self-induction, or the " electromagnetic mass " of 

 these two coils taken together. 



Let x be the value of the current in this wire at any instant, then Lx 

 will be its " electromagnetic momentum." 



Let (7 be the capacity of the condenser, and P the excess of potential of 

 the upper plate at any instant, then the quantity of electricity on the upper 

 plate is CP. 



Let p be the resistance of the additional conductor, and y the current in 

 it. We shall neglect the self induction of this current. 



We have then for this conductor, 



(i). 



For the charge of the condenser, 



dt 



.(2). 



For the current x, 



If we assume 



we find 



dx 



Mncosnt + Rx + L - 57 + P = 

 at 



x A cos (nt + a), 



(3). 



a = cot 



-~ 

 Cpn 



162 



