1899.] on Some Features of the Electric Induction Motor. 137 



be induced in coils through which an alternating magnetic field was 

 allowed to pass. 



By way of illustration, coils A and B were placed opposite and 

 parallel to one another, each being connected to a separate strip on 

 the oscillograph, in which the magnetic field was kept constant. 

 When an alternating current was passed through A, a current was 

 induced in B, and the two currents were shown on the screen in the 

 form of two curves overlapping each other. The explanation of the 

 overlapping was that the induced current in B was not in step with 

 the magnetism produced by A, but lagged behind it by an amount of 

 time equal to a quarter of a period. 



This lagging of the induced current behind the inducing mag- 

 netism bad an important bearing on the motor problem, because it 

 showed that it was not possible to make the magnetising coil A 



r\ 



A- 



r\ 



D- 



c 



\y 



U 



D 



G 



D 



induce in coil B a current suitable for producing a unidirectional 

 series of fluctuating impulses, since the necessary condition was that 

 the current in B should be in step with the magnetism produced 



If a second magnetising coil C could be used, in which the current 

 differed from that in A by a quarter of a period, it could be made to 

 induce currents in B which were in step with the magnetism pro- 

 duced by A. The intermediate coil B would then be subject to the 

 influence of two coils A and C, of which the former produced an 

 alternating magnetic field, and the latter an induced alternating 

 current in step with that field, the two together giving a series of 

 unidirectional fluctuating impulses. 



The magnetising coil A exerted the greatest force on the coil B 

 when the planes of the two coils were at right angles to each other, 

 and the coil C induced the greatest current in B when their planes 

 were parallel. Hence it followed that the best effect was obtained by 



