PROPERTIES OF STEEL MAGNETS. 



SECTION II. 



PROPERTIES OF STEEL MAGNETS. 



3. The steel magnets will be supposed to be slender 

 bars : usually they will be supposed to be straight. 



As a general rule, it is found impracticable to give 

 magnetism, admitting of careful experimental investiga- 

 tion, to a mass of steel of any form except that of a 

 long bar, straight or bent. (Detached bar-magnets are 

 usually made of uniform breadth throughout : compass- 

 needles, and other mounted magnets, are frequently 

 made with pointed ends, as having smaller moment of 

 inertia in proportion to the energy of their magnetism.) 

 The mathematical investigations which follow will be 

 confined to the case of straight bars, in which the length 

 greatly exceeds the breadth. General reference will 

 however be made to the horse-shoe magnet. 



4. Definition of a steel magnet : the definition some- 

 times applies to iron bars. 



The practical definition of a magnet is, "a bar of 

 steel which, when so suspended or so mounted on a fine 

 point that it can vibrate freely in the horizontal plane, 

 will take a definite direction ; and, if disturbed from 



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