MECHANICAL AND ELECTRICAL ANALOGIES. 



343 



vise 



Fig. a. 



A body of mass m is sup- 

 ported by a flat spring S, 

 clamped in a vise as shown 

 in Fig. a. A force F push- 

 ing sidewise on m moves it 

 a distance x, which is pro- 

 portional to f, according 

 to equation (16). When 

 started the body m will con- 

 tinue to vibrate back and 

 forth and the period r of its 

 vibrations is determined by 

 equation (19). 



wire 



body 



Fig. b. 



A body of moment of in- 

 ertia K is hung by a wire 

 as shown in Fig. b. A 

 torque T acting on the body 

 will turn the body and twist 

 the wire through an angle 

 <f>, which is proportional to 

 T, according to equation 

 (17). When started, th e 

 body will vibrate about the 

 wire as an axis and the 

 period T of its vibrations 

 is determined by equation 

 (20). 



Fig. c. 



A condenser C is con- 

 nected to the terminals of 

 a coil of inductance L as 

 shown in Fig. c. An elec- 

 tromotive force E acting 

 anywhere in the circuit 

 pushes into the condenser 

 a charge q, which is pro- 

 portional to E, according 

 to equation (18). When 

 started the electric charge 

 will surge back and forth 

 through the coil, constitut- 

 ing what is called an oscil- 

 latory current and the period 

 of one oscillation is deter- 

 mined by equation (21 ). 



