ELEMENTS OF ELECTRICAL ENGINEERING. 



frequency produces 100 amperes, and o>LI and I/coC are both 

 equal to 13,270 volts. 



36. Multiplication of current by resonance. When an induc- 

 tance and a condenser are connected in parallel,* as shown in Fig. 

 I 



1 



Fig. 68. Fig. 69. 



68, the total current delivered to the two divides, and the current 

 in each may greatly exceed the total current. The current rela- 

 tions are shown in the clock diagram Fig. 69. In this figure the 

 line OE represents the electromotive force between the branch 

 points a and b, the line 01^ represents the current that flows 

 through the inductance, the line <9/ 2 represents the current that 

 flows through the condenser, and the line 01 represents the total 

 current delivered by the alternator. 



The multiplication of current by resonance may be easily under- 

 stood by referring to the mechanical analog. A lever //, Fig. 70, 

 is suspended at its center by a bar b which oscillates up and down 

 through a small amplitude. One end of the lever carries a weight 

 L, and the other end is held down by a helical spring C. If the up 

 and down oscillations of the bar b take place at the proper frequency, 

 the lever will be set into a violent see-saw motion, and the veloc- 

 ities 7 L and 7 2 of the ends of the lever will greatly exceed the 



* Although the inductance and the condenser in Fig. 68 are in parallel with each 

 other with reference to the alternator, they are in series with each other in the short 

 circuit LaCb, and multiplication of cttrrent by resonance is due to the surging of cur- 

 rent to and fro around this short circuit so that the physical action of the inductance 

 and condenser during resonance is exactly the same in Fig. 68 as it is in Fig. 57. In 

 both cases the condition of resonance is given by equation (i), Art. 34. 



