ADVANCED ELECTRICITY AND MAGNETISM. 



to M. Therefore mH = , whence we have: 



M 



(i) 



in which H is the intensity of the magnetic field produced by 

 the pole M at a place which is r centimeters from M . 



- (F) /-^ r centimeters V F 



Fig. 8. 



10. Action of a magnetic field on iron or steel. When an iron 

 or steel rod is placed in a magnetic field, the length of the rod 

 being parallel to the direction of the field, the rod becomes a 

 magnet. Thus the iron rod AB in Fig. 9 is magnetized by the 

 field due to the large magnet pole N, the end A becomes a 

 south pole and the end "B becomes a north pole. 



N 



Fig. 9. 



The effect of the magnetic field on the iron rod AB is to magnetize it, the 

 end A becoming a south pole. 



ii. Behavior of a magnet in a magnetic field, (a) Behavior in 

 a uniform field. The equal and opposite forces which are exerted 

 on the poles of a magnet by a uniform magnetic field tend only to 

 turn the magnet into the direction of the field, the forces do not 

 tend to produce translatory motion of the magnet. Consider a 

 magnet / centimeters long placed in a uniform magnetic field 

 of which the intensity is H, the angle between the axis of the 



