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INVENTIONS OF NIKOLA TESLA.

increased by winding the disc with conductors o, closed uponthemselves and having a radial direction, whereby the magneticintensity of the poles of the disc will be greatly increased bythe energizing effect of the currents induced in the coils o by thealternating currents in coils n.

The cores of the disc and field may or may not be of differentmagnetic susceptibility—that is to say, they may both be of thesame kind of iron, so as to be magnetized at approximately thesame instant by the coils d; or one may be of soft iron and theother of hard, in order that a certain time may elapse betweenthe periods of their magnetization. In either case rotation willbe produced; but unless the disc is provided with the closed en-ergizing coils it is desirable that the above-described difference ofmagnetic susceptibility be utilized to assist in its rotation.

The cores of the field and armature may be made in variousways, as will be well understood, it being only requisite that thelaminations in each be in such direction as to secure the neces-sary angular displacement of the points of greatest attraction.Moreover, since the disc may be considered as made up of aninfinite number of radial arms, it is obvious that what is true ofa disc holds for many other forms of armature.