7. Electric resistance of metal
Resistance can be obtained by 
When the Electric
resistance R has length lm, cross section of uniform material 
. Here ρ is volume
resistivity, and the unit is Ω⋅m. The relation of 
is established when
volume resistivity of 0℃ is kept with 
, and volume resistivity
of 100℃ is kept with .
This 
is called as
mean temperature coefficient of volume resistivity within 0℃ and 100℃.
| Metal |  |
|||||
|---|---|---|---|---|---|---|
| -195℃ | 0℃ | 100℃ | 300℃ | 700℃ | 1200℃Others | |
|
Silver |
0.3 |
1.47 |
2.08 |
3.34 |
6.1 |
19.4 |
|
Gold |
0.5 |
2.05 |
2.88 |
4.63 |
8.6 |
31(1063℃) |
|
Calcium |
0.7 |
3.2 |
4.75 |
7.8 |
20 |
– |
|
Iridium |
0.9 |
4.7 |
6.8 |
10.8 |
22 |
33.5 |
|
Tungsten |
0.6 |
4.9 |
7.3 |
12.4 |
24 |
39 |
|
Zinc |
1.1 |
5.5 |
7.8 |
13.0 |
– |
37(500℃) |
|
Cobalt |
0.9 |
5.6 |
9.5 |
19.7 |
48 |
88.5 |
|
Potassium |
1.38 |
6.1 |
17.5 |
28.2 |
66.4 |
160 |
|
BrassBrass |
– |
6.3 |
– |
– |
– |
– |
|
Cadmium |
1.6 |
6.8 |
9.8 |
– |
– |
36.3(600℃) |
|
Osmium |
– |
8.1 |
11.4 |
17.8 |
30.4 |
46 |
|
Tin |
2.1 |
11.5 |
15.8 |
50 |
60 |
72 |
|
Tantalum |
2.5 |
12.3 |
16.7 |
25.5 |
43.0 |
61.5 |
|
Chromium |
0.5 |
12.7 |
16.1 |
25.2 |
47.2 |
80 |
|
Bronze |
– |
13.6 |
– |
– |
– |
– |
|
Thallium |
3.7 |
15 |
22.8 |
38 |
85 |
88(800℃) |
|
Strontium |
5 |
20 |
30 |
52.5 |
94.5 |
– |
|
Alumel |
– |
28.1 |
34.8 |
43.8 |
53.2 |
65.1 |
|
Antimony |
8 |
39 |
59 |
– |
114 |
123.5(1000℃) |
|
Zirconium |
7.3 |
40 |
58 |
88 |
125 |
110(1000℃) |
|
Constantin |
– |
49 |
– |
– |
– |
– |
|
Invar |
75 |
 |
||||
|
Mercury |
5.8 |
94.1 |
103.5 |
128 |
214 |
630 |
|
Bismuth |
35 |
107 |
156 |
129 |
155 |
172(1000℃) |
|
Copper« |
0.2 |
1.55 |
2.33 |
3.6 |
6.7 |
21.3(1083℃) |
|
Palladium |
1.73 |
10.0 |
13.8 |
21 |
33 |
42 |
|
Nichrome |
– |
107.3 |
108.3 |
110.0 |
110.3 |
– |
|
Rubidium |
2.2 |
11.0 |
27.5 |
48 |
99 |
260 |
|
Thorium |
3.9 |
14.7 |
20.8 |
32.5 |
53.6 |
68 |
|
|
– |
18.7 |
21.8 |
– |
– |
– |
|
Lead |
4.7 |
19.2 |
27 |
50 |
108 |
126(1000℃) |
|
Aluminum |
0.21 |
2.50 |
3.55 |
5.9 |
24.7 |
32.1 |
|
Berylium |
– |
2.8 |
5.3 |
11.1 |
26 |
– |
|
Arsenic |
5.5 |
26 |
– |
– |
– |
– |
|
Magnesium |
0.62 |
3.94 |
5.6 |
10.0 |
27.7 |
28.7(900℃) |
|
Sodium |
0.8 |
4.2 |
9.7 |
16.8 |
39.2 |
89 |
|
Rhodium |
0.46 |
4.3 |
6.2 |
10.2 |
20 |
33 |
|
German silver |
– |
40 |
– |
– |
– |
– |
|
Manganin |
– |
41.5 |
– |
– |
– |
– |
|
Molybdenum |
0.7 |
5.0 |
7.6 |
12.7 |
23.3 |
37.2 |
|
Nickel |
0.55 |
6.2 |
10.3 |
22.5 |
40 |
109(1500℃) |
|
Chromel P |
– |
70.0 |
72.8 |
79.3 |
89.3 |
100.1 |
|
Indium |
1.8 |
8.0 |
12.1 |
36.7 |
47 |
55(1000℃) |
|
Lithium |
1.04 |
8.55 |
12.4 |
30 |
40.5 |
53 |
|
IronPure |
0.7 |
8.9 |
14.7 |
31.5 |
85.5 |
122 |
|
Platinum |
1.96 |
9.81 |
13.6 |
21.0 |
34.3 |
48.3 |
