Specific resistance or resistivity

In order to understand the behaviour of the materials, it is necessary to study certain properties like (a) Resistivity (b) Conductivity and (c) conductance.

The resistance (R) of a conductor depends on its length, area of cross section.

In the above equation if l=1m and A=1sq.m, then p(rou)=R. There is the difference between the resistance and resistivity i.e., resistance is the bulky property of a material and resistivity is specific property of the material.Since, specific resistance is proportionality constant, so that it is independent of length and area of cross section for that material.

For conductors, the specific resistivity like follows


From the above figure we found that for mercury, the resistivity is high.
For semi conductors, insulators resistivities like follows

From the above the above tables, we see that resistivity of insulators is about 10power22 times the metallic conductors. Since metals like silver, copper and aluminium have lowest resistivities, so that there are used in manufacture electric cables, connecting wires etc.