80 ELEMENTS OF ELECTRICAL ENGINEERING. 



cuit which has resistance only, has the same wave shape as the 

 electromotive force, inasmuch as the current is at each instant 

 equal to e/R, that is, the current curve may be considered as 

 representing the electromotive force curve. Thus the oscillo- 

 graph curve A in Fig. 71 is the electromotive force curve of 

 an alternator whose armature winding is placed in slots, the 

 effect of the slots being to introduce slight fluctuations in the 

 the electromotive force wave, as shown by the curve A. 



The effects of inductance. A circuit having inductance is a cir- 

 cuit having electrical inertia, and very rapid variations of electro- 

 motive force produce but little variation in the current on account 

 of the inertia. This is shown by the oscillograph curve C in 

 Fig. 71, which is the curve of the current which is produced in 

 an inductance coil (without an iron core) by the electromotive 

 force A. Any non-harmonic alternating electromotive force pro- 

 duces an approximately harmonic current in a highly inductive 

 circuit (with no iron core). 



The effects of a condenser. Any quick change of electromotive 

 force produces a sudden rush of current into or out of a con- 

 denser, and therefore rapid variations of electromotive force pro- 

 duce large variations of current in a circuit which contains a 

 condenser. This is shown by the oscillograph curve B in Fig. 

 71, which is the curve of current produced by the electromotive 

 force AA in a circuit containing a condenser. 



The effect of inductance in giving a smooth current curve 

 and the effect of capacity in giving a current in which the irregu- 

 larities of the electromotive force are greatly exaggerated are 

 very strikingly shown by Figs. 72 and 73. Fig. 72 shows a 

 peaked electromotive force curve produced by an alternator hav- 

 ing a few very large armature slots, the curve A A, Fig. 73, is 

 the same as the curve of Fig. 72, the curve CC is the fairly 

 smooth curve of current produced in an iron-less inductance by 

 the electromotive force AA y and the extremely irregular curve 

 BB is the curve of current produced in a condenser by the 

 electromotive force A A. 



