CHARACTERISTIC CURVES. 



391 



the Wood arc lighting generator of which the volt-ampere char- 

 acteristic is shown in Fig. 22. 



The ampere-ohm characteristic is derived from the volt-ampere 

 characteristic as follows : Lay off the abscissa of each point / of 



Amperes 



Ohms 



Fig. 23. 



the volt-ampere characteristic, Fig. 22, as the ordinate of the 

 corresponding point p 1 of the ampere-ohm characteristic and 

 lay off in each case the ratio EJI, see Fig. 22, as the abscissa 

 of/. 



28. Examples showing applications of the external characteristic 

 of a series generator. The examples to be given depend upon 

 the use of what is called the receiving circuit characteristic. This 

 is a curve showing the relation between the electromotive force 

 acting on the receiving circuit and the current produced in the 

 receiving circuit by this electromotive force. 



When the receiving circuit consists simply of a resistance R r , 

 the electromotive force required to produce a current / is equal 

 to R r l, and the receiving circuit characteristic is a straight line, 

 AB, as shown in Fig. 24. 



