6 ELEMENTS OF ELECTRICAL ENGINEERING. 



Hydraulic analogy of magnetic field. (a] A steadily moving 

 liquid has at each point a definite velocity in a definite direction 

 and the trend of a steadily moving liquid may best be pictured in 

 the mind by imagining curved lines drawn through the liquid, 

 these lines being at each point in the direction of the velocity o 

 the liquid at that point. Such lines are called stream lines. 

 Where the stream lines are crowded together the velocity of the 

 liquid is great, and where the stream lines are spread apart the 

 velocity of the liquid is small. When the stream lines are 

 parallel straight lines the velocity of the liquid is everywhere the 

 same in value and in direction, and the motion of the liquid is 

 said to be homogeneous or uniform. 



Fig. 1. 



(&) A magnetic field has at each point a definite intensity in a 

 definite direction, and the trend of a magnetic field may best be 

 pictured in the mind by imagining curved lines drawn through 

 the field, these lines being at each point in the direction of the 



