348 HOW ELECTRICITY IS MADE ON A LARGE SCALE 



A magnet possesses lines of force, and as the magnet 

 moves toward the coil it carries lines of force with it, and the 

 coil is cut, so to speak, by these lines of force. As the mag- 

 net recedes from the coil, it carries lines of force away with 

 it, this time reducing the number of the lines which cut the 

 coil. 



320. A Test of the Preceding Statement. We will test the 

 statement that a magnet has electric properties by another ex- 

 periment. Between the poles of a strong magnet 

 suspend a movable coil which is connected with 

 a sensitive galvanometer (Fig. 237). Starting 

 with the coil in the position of Figure 228, when 



r- / | many lines of force pass through it, let the 

 coil be rotated quickly until it reaches the posi- 

 tion indicated in Figure 238, when no lines of 

 force pass through it. During the motion of the 

 coil, a strong deflection of the galvanometer is 

 observed ; but the deflection ceases as soon as the 



FIG. 238. As ... 



long as the coil ceases, to rotate. It, now, starting with the 

 coil rotates be- p OS iti O n of Figure 238, the coil is rotated forward 



tween the v 



poles of the to its starting point, a deflection occurs in the 

 renf flows CUr ~ PP s i te direction, showing that a current is pres- 

 ent, but that it flows in the opposite direction. 

 So long as the coil is in motion, it is cut by a varying 

 number of lines of force, and current is induced in the coil. 

 The above arrangement is a dynamo in miniature. By 

 rotation of a coil (armature) within a magnetic field, that is, 

 between the poles of a magnet, current is obtained. 



In the motor, current produces motion. In the dynamo, 

 motion produces current. 



321. The Dynamo. As has been said, the arrangement of 

 the preceding Section is a dynamo in miniature. Every 

 dynamo, no matter how complex its structure and appear- 



