Resistivity Density Products
In some applications where the weight of an item is very important resistivity density products are more important than absolute low resistivity- it is often possible to make the conductor thicker to make up for a higher resistivity; and then a low resistivity density product material (or equivalently a high conductance to density ratio) is desirable. For example, for long distance overhead power lines— aluminium is frequently used rather than copper because it is lighter for the same conductance.
| Material | Resistivity (nΩ•m) | Density (g/cm3) | Resistivity-density product (nΩ•m•g/cm3) |
|---|---|---|---|
| Sodium | 47.7 | 0.97 | 46 |
| Lithium | 92.8 | 0.53 | 49 |
| Calcium | 33.6 | 1.55 | 52 |
| Potassium | 72.0 | 0.89 | 64 |
| Beryllium | 35.6 | 1.85 | 66 |
| Aluminium | 26.50 | 2.70 | 72 |
| Magnesium | 43.90 | 1.74 | 76.3 |
| Copper | 16.78 | 8.96 | 150 |
| Silver | 15.87 | 10.49 | 166 |
| Gold | 22.14 | 19.30 | 427 |
| Iron | 96.1 | 7.874 | 757 |
Silver, although it is the least resistive metal known, has a high density and does poorly by this measure. Calcium and the alkali metals have the best resistivity-density products, but are rarely used for conductors due to their high reactivity with water and oxygen. Aluminium is far more stable. Two other important attributes, price and toxicity, exclude the (otherwise) best choice: Beryllium. Thus, aluminium is usually the metal of choice when the weight of some required conduction (and/or the cost of conduction) is the driving consideration.
Read more about this topic: Electrical Resistivity And Conductivity
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