Electro-magnet, Annular.
An electro-magnet consisting of a cylinder with a circular groove cut in
its face, in which groove a coil of insulated wire is placed. On the
passage of a current the iron becomes polarized and attracts an armature
towards or against its grooved face. The cut shows the construction of
an experimental one. It is in practice applied to brakes and clutches.
In the cut of the electro-magnetic brake (see Brake, Electro-magnetic),
C is the annular magnet receiving its current through the brushes, and
pressed when braking action is required against the face of the moving
wheel. The same arrangement, it can be seen, may apply to a clutch.