IN CYLINDRICAL CONDUCTORS, ETC. 
87 
Table. —Effective Resistance of Single Layer Solenoidal Coils. 
Coil. 
Radius 
a 
Length 
b 
Turns 
Dia¬ 
meter 
of 
Direct 
Current 
Induct¬ 
ance 
L 
Experimental. 
Calcula¬ 
ted 
Obsr. 
Range 
of 
Wave- 
cm. 
cm. 
n. 
wire 
d mm. 
R ohms. 
micro¬ 
henries. 
A. 
B. 
A. 
length 
metres. 
1 
15-5 
1-8 
7 
2-2 
36 
9-5 
2-14xl0 4 
10-4 
L.H. 
2 
9-7 5 
2-6 
11 
2 
0-0382 
43 
11-8 
2-15 xlO 4 
11-2 
L.H. 
100 
3500 
3 
11-3 
2-0 
13 
0-71 
0-425 
75 
25-1 
7-4 x10 4 
25-5 
N.P.L. 
150 
600 
4 
10-0 
6-5 
18 
3 
— 
80 
14-3 
7-0 x10 4 
13-2 
L.H. 
— 
5 
9-8 
2-ls 
15 
1-1 
— 
84 
25-5 
7-0 xlO 4 
25-6 
L.H. 
— 
6 
11*75 
1-0 
13 
0-71 
0-444 
100 
49-0 
6-8 xlO 4 
50 
N.P.L. 
200 
600 
7 
8-7 5 
7-3 
40 
1-62 
0-193 
320 
56 
1-7 xlO 6 
55 
N.P.L. 
600 
1500 
The direct current resistances were not known in the cases of the coils 1, 4, 5. For 
the calculation of A, their values were deduced from the dimensions of the coils using the 
resistivity of copper as given by the known direct current resistance of Coil 3. 
It was to throw some light upon the properties of the second term (B/x 2 ) in Linde. - 
mann’s equation that the three coils marked N.P.L. were measured. Coil No. 6, which 
was wound with D.S.C. wire and held together by wax and silk without any other frame, 
was measured first to confirm Lindemann’s results. The observations are given below 
for this coil and are typical. In the Table, R 4 is the measured resistance of the coil. 
R' is obtained from R t by dividing by (1 — W 2 LC) 2 , where C is the measured self 
capacity of the coil. The values of A and B are deduced by plotting R'^/x against X~ 3/ ’ 2 
(formula (71)). 
Coil No. 6. L = 100-0 microhenries. C = 20 /ifx F. 
X 
metres. 
Ri 
ohms. 
R' 
ohms. 
a/ jk. 
B/X 2 . 
R' 
(formula (71)). 
206 
7-2 
5-0 0 
3-4. 2 
1 * 6i 
5-0 3 
229 
6-2 
4-6 4 
3-2 4 
1*3! 
4-5 5 
260 
5-2 
4-l 6 
3-0 4 
l-0i 
4-0 5 
294 
4-3 
3-6! 
2-8 5 
0-7 9 
3-6 4 
350 
3-5 
3-l 0 
• 2-6 4 
0-5 6 
3-2 0 
463 
2-8 
2-6., 
2-2 s 
0-3o 
2-6 0 
500 
2-6 
2-4 c 
2- R 
0-2 t 
2-4 6 
543 
2-5 
2-3 s 
2*1 0 
0-2 3 
2-3 3 
584 
2-3 
2-3 0 
2-0, 
0-2 0 
2-2o 
