IN CYLINDRICAL CONDUCTORS, ETC. 
91 
If close winding is employed (keeping ajb = 1*6), the losses at high frequencies will be 
42 per cent, greater than when the proper spacing is employed. Fig. 9 summarizes the 
R' = Alternating current resistance, L = Inductance. 
t = R'/L , t o = Minimum R'/L. 
z = 830/ VR'oA , R' 0 = D.C. resistance in ohms per 1,000 yards. 
A = Wave-length in metres. 
Frequency high if z >2. 
At high frequencies best shape is a/b = 1-6, best spacing (average) is D jd — 2. 
At low frequencies best shape (average) is a/b = 1*4 and close winding is the best. 
results of this section. The full crave gives the best spacing, and the broken curves show 
the limits allowable if losses 1 per cent, and 5 per cent, greater than the minimum losses 
are permissible. The figure may be used to grade coils for different ranges of frequency. 
Thus the 5 per cent, limit will be attained if below z = 2 we make a/b = 1-4* and 
employ close winding, and above z — 2 we make ajb — 1-6 and space the wire so that 
* Between z = 0 and z = 1 • 6 the best value of a/b rises from 1 • 2s (the steady current value) to 1-6. The 
value a lb = 1- 4 will never produce a loss exceeding by 0-2 per cent, the minimum loss. 
o 2 
