12

INVENTIONS OF NIKOLA TESLA.

c c being nil, since these coils are included in the circuit ofcoil c.

In Fig. 2, the armature coils are shown in a more advancedposition, one-eightli of one revolution being completed. Fig.2a illustrates the corresponding magnetic condition of the ring.At this moment the coil c ( generates a current of the same di-

Fig. 3.

Fig. 3a.

rection as previously, but weaker, producing the poles r> 1 uponthe ring; the coil c also generates a current of the same direc-tion, and the connections may be such that the coils c c producethe poles n x, as shown in Fig. 2a. The resulting polarity isindicated by the letters n s, and it will be observed that thepoles of the ring have been shifted one-eighth of the peripheryof the same.

In Fig. 3 the armature has completed 'one quarter of onerevolution. In this phase the current in coil c is a maximum, andof such direction as to produce the poles n s in Fig. 3 a, whereasthe current in coil cy is nil, this coil being at its neutral position.

Fig. 4.

Fig. 4a.

The poles n s in Fig. 3 a are thus shifted one quarter of thecircumference of the ring.

Fig. 4 shows the coils c c in a still more advanced position,the armature having completed three-eighths of one revolution.At that moment the coil c still generates a current of the samedirection as before, but of less strength, producing the compar-