194 



ADVANCED ELECTRICITY AND MAGNETISM. 



vise 



Fig. 131. 



A body of mass m is 

 supported by a flat spring 

 S, clamped in a vise as 

 shown in Fig. 131. A 

 force F pushing sidewise 

 on m moves it a distance 

 x, which is proportional to 

 F, according to equation 

 (16). When started, the 

 body m will continue to 

 vibrate back and forth 

 and the period r of its 

 vibrations is determined 

 by equation (19). 



wire 



I ** I 



Fig. 132. 



A body of moment of in- 

 ertia K is hung by a wire 

 as shown in Fig 132. A 

 torque T acting on the 

 body will turn the body 

 and twist the wire through 

 an angle <, which is pro- 

 portional to T, according 

 to equation (17). When 

 started, the body will 

 vibrate about the wire as 

 an axis and the period T 

 of its vibrations is deter- 

 mined by equation (20). 







Fig. 133. 



A condenser C is con- 

 nected to the terminals of 

 a coil of inductance L as 

 shown in Fig. 133. An 

 electromotive force E 

 acting anywhere in the 

 circuit pushes into the 

 condenser a charge q, 

 which is proportional to E, 

 according to equation (18). 

 When started, the electric 

 charge will surge back and 

 forth through the coil, con- 

 stituting what is called an 

 oscillatory current and tin- 

 period of one oscillation is 

 determined by equation 

 (21). 



Note. Frictional opposition to the motion in Figs. 131 and 

 132, and the resistance of the circuit in Fig. 133 are supposed to 

 be zero. 



