ELEMENTARY THEORY OF ELECTROMAGNETISM. 63 



end A will move with large 

 back and forth velocity, and 

 the end B will move with 

 small back and forth velocity; 

 but end B will exert a large 

 force. 



In fact, if we ignore the slight 

 movement of the heavy body, we 

 will have: 



and 



e" V 







i" ~ i" 



(i) 



(3) 



where, at any instant, e' is 

 the force exerted on end A, 

 i' is the velocity of end 

 e" is the force exerted 

 end B, and i" is the velocity 

 of end B. 



A, 

 by 



former. Then a large current 

 flows back and forth through 

 the primary coil and a small 

 current flows back and forth 

 through the secondary coil ; but 

 the secondary coil acts upon 

 the receiving circuit with a 

 large electromotive force. 



In fact, if we ignore the small 

 current through the primary coil 

 which magnetizes the iron core, 

 we will have: 



7' = ^> (2) 



and 



777 = ~^7 (4) 



as explained in part in Art. 30: 

 where, at any instant, e' is the 

 electromotive force acting on 

 the primary coil, i' is the cur- 

 rent flowing through the pri- 

 mary coil, e" is the electro- 

 motive force induced in the 

 secondary coil, and i" is the 

 current flowing through the 

 secondary coil. 



The analogy above outlined is complete, but it is not worth while to develop 

 it in full. Thus the movement of the massive body M is exactly analogous to the 

 magnetizing current in a transformer, and the mass of the lever itself leads to 

 behavior which is exactly analogous to magnetic leakage in a transformer. This 

 latter is indeed developed in Art. 43; but from a point of view somewhat different 

 from the usual discussion* of magnetic leakage in transformer theory. 



* See Chapter XI, Elements of Electrical Engineering, Vol. II., Franklin and Esty, 

 The Macmillan Co., 1908. 



