The following table gives the data for a few metals:
| Substance. | Specific Resistance in Microhms. | Specific Conductivity. |
| Silver | 1.609 | 100. |
| Copper | 1.642 | 96. |
| Gold | 2.154 | 74. |
| Iron (soft) | 9.827 | 16. |
| Lead | 19.847 | 8. |
| German Silver | 21.470 | 7.5 |
| Mercury (liquid) | 96.146 | 1.6 |
The specific resistance of copper is therefore:
1.642 / 1,000,000 ohms, or 1.642 microhms.[6]
Divided Circuits.—If a circuit be divided, as in fig. 83, into two branches at A, uniting again at B, the current will also be divided, part flowing through one branch and part through the other.
The relative strength of current in the two branches will be proportional to their conductivities.
This law will hold good for any number of branch resistances connected between A and B. Conductivity is, as shown before, the reciprocal of resistance.
EXAMPLE—If, in fig 83, the resistance of R = 10 ohms, and R′ = 20 ohms, the current through R will be to the current through R′ as 1⁄10 to 1⁄20; or, as 2:1, or, in other words, 2⁄3 of the total current will pass through R and 1⁄3 through R′. The joint resistance of the two branches between A and B will be less than the resistance of either branch singly, because the current has increased facilities for travel. In fact, the joint conductivity will be the sum of the two separate conductivities.
Taking again the resistance of R = 10 ohms and R′ = 20 ohms, the joint conductivity is
1⁄10 + 1⁄20 = 3⁄20