68 



ADVANCED ELECTRICITY AND MAGNETISM. 



when the car P is held fast. When these two frequencies are 

 adjusted to equality, the primary and secondary systems are 

 said to be tuned to each other. 



The ratio of transformation of the transformer in Fig. 52 is 

 represented by the ratio of the two lever arms / and /'. 



i 



Fig. 53. 



When the weight W is very large or when the weights of the 

 cars P and 6" are small, we have what is called close coupling. 

 When the weights of the cars P and S are large, or when the 

 weight W is small, we have what is called loose coupling. 



(a) When the primary system PC is set oscillating, a series 

 of force impulses is transmitted to the secondary system SC' 

 by the lever, and the secondary system is quickly set into oscilla- 

 tion. 



(b) When the primary and secondary systems are in tune with 

 each other, the whole of the energy of the oscillating primary 

 system is transformed into the secondary system, and the primary 

 system comes momentarily to rest. Then the energy is trans- 

 formed back from secondary to primary and so on repeatedly. 



(c) When the primary and secondary systems are not in tune 

 with each other, a definite fractional part only of the energy of 

 the primary system is transformed to the secondary. This 



