. Electricity simplified. The practice and theory of electricity ... ot conversant with electricity to utilize themagnet as a source of power. If this were possible,then perpetual motion would be discovered. Inqui-ries are often propounded as to what substance willcut off magnetic influence. This can only be doneby some polarizable material which in itself willconstitute an armature. The mere attraction of anarmature and its retention only requires the exer-tion of force; the motion of an armature against aresistance such as its lifting through space re-quires energy. This distinction is impor
. Electricity simplified. The practice and theory of electricity ... ot conversant with electricity to utilize themagnet as a source of power. If this were possible,then perpetual motion would be discovered. Inqui-ries are often propounded as to what substance willcut off magnetic influence. This can only be doneby some polarizable material which in itself willconstitute an armature. The mere attraction of anarmature and its retention only requires the exer-tion of force; the motion of an armature against aresistance such as its lifting through space re-quires energy. This distinction is important andtoo little appreciated. A magnet holding its arma-ture attracted does no work. When a bar of iron is wound with wire, insulated 86 ELECTRICITY SIMPLIFIED. or otherwise prevented from touching the iron andwith its spirals not touching each other, the iron be-comes a magnet, It attracts iron and steel, each endrepels one pole and attracts the other pole of a com-pass needle or other magnet, and it shows lines offorce reaching from pole to pole and in general. v^j^m. y Fig. 19.—Electro-Magnet Developing Lines of force. the indications of possessing magnetism or of beingpolarized. If instead of iron a piece of steel is taken andtreated thus, the effects are the same in general, ex-cept that a large portion of the imparted magnetismis permanent, and remains after the current hasceased. It is found also that the magnet thus made pos-sesses north and south poles, or, if suspended by a finethread, or if floated on a cork on water, will point AMPERES THEORY. 87 north and south approximately, and the same endwill always seek the north pole and the other thesouth pole of the earth. The poles are found to beformed on one or the other end, according to the di-rection of the current which excited the bar to mag-netism. If the observer is imagined as facing one of thepoles of a bar wound with wire as described, it isevident that the current may be supposed to go inthe direction of t
Size: 1857px × 1346px
Photo credit: © Reading Room 2020 / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1800, bookdecade1890, bookidel, booksubjectelectricity
