DIRECT-CURRENT DYNAMOS AND MOTORS. 5 
53. 
54. 
55. 
60. 
61. 
62.. 
63. 
64 
What is the average percentage of power loss in a 75.K. W. 
machine? 
Give the usual limits of the actual power loss (in kilowatts) 
of a 200 K. W. dynamo. 
From Table 3, Instruction Book, find the usual limits and 
the average of the power loss in a 10 K. W. dynamo.. 
Give the formula for the diameter of a drum armature hav- 
ing a cooling surface proportional to its capacity W. 
State the corresponding formula for a ring armature. 
What value of s should be used in the formula for drum 
armatures referred to in Question 56? 
Give the value of the specific cooling surface employed in 
connection with ne formula for ring armatures referred 
to in Question 5 a5. 
Give the average ratios (a) of length to diameter, and (b) 
of radial thickness to diameter, for a 10-foot ring arma- 
ture, using Table 4, Instruction Book. 
From the answer to the preceding question find the average 
length and radial thickness of aring armature n> aha a. 
diameter of 10 feet. 
State the approximate shape ratios of a ring armature 20 
inches in diameter. 
What is the average shape ratio, m, and the length, La, of 
a drum armature 8 inches in diameter? 
Give the approximate average length of a drum armature 
having a diameter of 36 inches. 
