DIRECT-CURRENT DYNAMOS AND MOTORS. 3 
25. 
26. 
2%. 
28. 
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30. 
31. 
32. 
33. 
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35. 
36. 
37. 
38. 
- What is understood by the effective cross-section of the 
armature core? 
Name the advantages of toothed armatures. 
State the disadvantages of toothed armatures. 
How should the slots of a toothed armature be proportioned 
so as to avoid the generation of eddy currents in the pole 
pieces? 
Name some expedients employed to reduce the eddy current 
tendency due to improperly proportioned toothed arma- 
tures. 
What are the objections to perforated armatures? 
Name the chief points to be considered in determining the 
size of an armature. 
Give the formula’ for the peripheral velocity of an armature, 
‘Express the diameter of an armature in terms of its periphe- 
ral velocity, v, and its revolving speed, v,. 
What are the limits of the peripheral velocity in practical 
machines? 
Give the average value of v for high-speed ring machines. 
What is the average peripheral velocity of medium-speed 
ring machines? 
State the average of v for low-speed machines. 
What is the average circumferential velocity of drum 
armatures? 
Give the approximate armature velocity fora high-speed 
ring machine of 25 K. W. capacity. 
