ARMATURE (Lat. armature, armor; Ger. Anker). The mass of iron or other magnetizable substance that is placed in contact with the pole or poles of a magnet, or in proximity thereto. In the ease of a permanent magnet of the horse shoe pattern, the armature may be of soft iron and act as the keeper to help retain and preserve the magnetism by completing the magnetic cir cuit through the two poles. The armature of an electromagnet is placed near its poles, and when ever a current of electricity is sent through the coils of the latter, is attracted or repelled. If the armature is a piece of soft iron, attraction always takes place, and on this principle is based the action of the electric bell, the tele graph sounder, and other forms of electrical ap paratus. Such an armature, as soon as the flow of the current ceases, returns to its normal posi tion under the action of gravity or of a spring.
If the armature is a permanent steel magnet or another electro-magnet, it may move either toward or away from the main electro-maguet, depending on its polarity, and in that case is known as a polarized armature. In dynamo electric machinery, the tern; armature is used to designate that portion of the machine in which the differences of electric potential pro ducing the current are generated. and is gener ally employed to describe the part which is re volved between the poles of the field magnets. The name is used in this connection, since the iron cores on which the coils comprising the armature are wound afford a magnetic connec tion between the poles of the field magnets, just as is done by the keeper or armature of the horse shoe magnet. See :MAGNETISM and DY NA MO ELECTRIC MACHIN ERY.