238] INDUCTION OF CURRENTS. 483 



The power when R 2 is zero is only 



which, for high frequencies, may be much less than the maximum*, 

 being, when co is great enough, sensibly equal to the maximum 



value multiplied by 



2^ 



The second of equations (9) gives 

 B - Mia 



The modulus of the quotient, being the quotient of the moduli, 



\B Mto 



(16) 



shows that the amplitude J 2 (0) of the secondary current is equal to 

 the amplitude of the primary I-f* multiplied by Mco divided by the 

 impedance of the secondary. Inserting the values of R', L ', from 



(17) 



gives for / 2 (o) , 



(18) \B\=If\ 



In the case of no magnetic leakage this becomes 



and if we may neglect R^L^ or R 2 /L 2 a) in comparison with unity 

 we have the simple form 





(20) 



This is the practical equation of the transformer. By 231, (5) 

 and (6), we have 



* J. J. Thomson, Elements of the Mathematical Theory of Electricity and 

 Magnetism, p. 409. 



312 



