DIRECT-CURRENT DYNAMOS AND MOTORS. 15 
railway generator, having 2,400 armature conductors, 
if at 175 revs. per min. its voltage is 550, and if the 
length of the armature is 134 inches. 
148. What should be the internal diameter of a 6-pole ring 
armature whose external diameter is 17 inches and 
whose length is 5 inches, if the total armature flux is 
2,700,000 lines? 
149. Give the formula for the total length of conductor on a 
drum armature. 
150. What are the usual limits of the numerical value of the 
factor k in the formula matonred. to in the preceding 
question? 
151. Compute the average total length of wire on a smooth 
drum armature, 8 inches in diameter and 15 inches 
long, if its winding consists of 66 coils, each having 2 
turns. 
152. What is the total length of conductor of a toothed drum 
armature, 8 inches in diameter, 14 inches long, having 
36 slots, each holding 8 wires, the depth of the slots 
b. ing 1 inch? 
153. Define a spirally wound armature. 
154. State the formula for the total length of wire on a 
spirally wound ring armature. 
155. A spirally wound smooth-core armature has an external 
core diameter of 18 inches, and an internal core diame- 
ter of 11 inches, and a length of 15 inches; it contains 
560 conductors occupying an average height of 4 inch; 
what is the average total length of wire? 
156. Find the approximate total length of wire on a 27-inch 
armature, 12 inches long, which is wound with 144 
formed coils, each consisting of 4 turns and spanning 
one eighth of the circumference. 
15%. A 14-pole toothed armature is wound with formed coils. 
Its diameter is 7 feet; its length, 174 inches; it has 
