rir ii 10 



how the current has to be increased by reducing A' > 

 order to obtain a balance. 



Decrease the load and observe the diminished 

 current required t'.-r a Uilamv. 



K.-.-J, the load constant, ami diminish the resistance; 

 note ( uporary increase of current ; (!) the direct i< >n 



of rotation, say clockwise; (r) the tendency >f the current 

 t" resume it- \alue. 



I. Keep the load constant, and increase the resistance; 

 note () the temporary decrease of current ; ('> tin- din 

 of rotation. now counter-clockwise ; (.-) tin- tnidrncy of the 

 current to ivMime its previous value. 



< 'ut the c. -rd and notice luiw the armature speeds 



Maximum speed. Take the speed and the t 

 at the brashes. Deduce A/, calculate the torque* il>r th<- 

 :its previously observed, and see how th.-\ correspond 

 with the 1 1 >rt|ii<ti obtained ly measuring the pulley diameter. 

 itnd multiplying ly the weights used. 



TheiH- c-ixiiiitiuns might be rea!Uel in the case of 

 a lift, thr unbalanced weight of a car taking the place 

 .f tin- wi-iirht* in thr r\|wrim*-nt. A rrrtain curn-nt 

 u required to hold the car in position. If the resi- 

 ts decreased or the tension of the line increased, 

 the car rises. If the resistance is increased or ill- 

 tension decreased, the car descends, the lin-cti<>n nf 

 rotation being reversed, and the dynamo acting as a 

 generator but without reversal *>f runvnt. ih.- induced 

 tension helping that of the lin**. 



Suppose, on the other hand, that the tension and ill-- 

 resistance were constant, and the load gradually increased. 

 The speed would diminish until, for a certain load, tin- 

 motor would cume to rest, the renditions Mintnfrt being 



S 



