Use the data in the given table, to answer the following:
Table. Resistivities of some substances at 20°C
|
Class |
Substances |
Resistivity (in ohm m) |
|
Metals(Conductors) |
Silver Copper Aluminium Tungsten Nickel Iron Chromium Mercury Manganese |
1.60 x 10–8 1.62 x 10–8 2.63 x 10–8 5.20 x 10–8 6.84 x 10–8 10.0 x 10–8 12.9 x 10–8 94.0 x 10–8 1.84 x 10–8 |
|
Alloys (Conductors) |
Constantan |
49 x 10–6 |
|
Manganin |
44 x 10–6 |
|
|
Nichrome |
100 x 10–6 |
|
|
Semiconductors |
Germanium Silicon |
0.46 2.300 |
|
Insulators |
Glass Hard rubber Ebonite Diamond Paper (dry) |
1010– 1014 1013 – 1016 1015 – 1017 1012 – 1013 1012 |
(a) Which among iron and mercury is a better conductor?
(b) Which material is the best conductor?
From the table given above, we have
(a) Resistivity of iron = 10.0 x 10-8 Ω m
Resistivity of mercury = 94.0 x 10-8Ω m
Since, iron has lower resistivity than mercury therefore, iron is a better conductor than mercury.
(b) As, silver has the lowest resistivity (= 1.60 x 10–8 Ω m), so silver is the best conductor.
