INDUCED CURRENTS 



157 



the circuit, and back to the armature a through the 

 other brush. 



The energy by which the dynamo is run is usually 

 furnished by a steam engine or water power. It is 

 applied at the axle, being used to turn the armature. 

 This turns at a high speed, the strength of the current 

 generally increasing as its speed is raised. 



181. Direction of the Current. The whole circuit, 

 outside and within the dynamo, is one continuous path, 



FIG. 114 



the outside conducting wire being joined to that of the 

 armature through the brushes 5, b (Fig. 114). Now the 

 direction of the current through this circuit depends 

 upon the direction in which the armature a moves 

 across the lines of force ; and since each part of a cuts 

 these lines in one direction during one half of a turn, 

 and in the opposite direction the other half, the current 

 will travel through the circuit first in one direction and 



