The electrical resistivity of a material is the measure of its resisting power to the flow of an electric current. Resistivity is represented by the following symbols.
Resistivity symbol: ρ
List of Contents
Resistivity Formula
The resistivity of a metallic conductor can be expressed using the equation given below.
Resistivity Formula: ρ = A.R / l
where
ρ = Resistivity
A = Cross-sectional area of conductor
l = length in meters
Besides the above-given formula, resistivity can also be expressed by the following relation:
ρ = E/J
where E is magnitude of electric field
and J is energy in joules
Resistivity Chart for Some Materials
The resistivities of some most common materials existing in nature are given below in resistivity chart:
| Material | Resistivity (ρ in Ω-m) @ 20° |
| Silver | 1.645 X 10-8 |
| Copper | 1.723 X 10-8 |
| Gold | 2,443 X 10-8 |
| Aluminum | 2.825 X 10-8 |
| Tungsten | 5.485 X 10-8 |
| Iron | 12.30 X 10-8 |
| Lead | 22 X 10-8 |
| Mercury | 95.8 X 10-8 |
| Nichrome | 99.72 X 10-8 |
| Carbon | 3500 X 10-8 |
| Germanium | 20-2300 |
| Silicon | 500 |
Good to know
- The resistivity material is dependent on the impurities within the materials
- The resistivity of a material can be used to calculate resistance of material provided that area of its cross sectional and length is known
Solved Examples on Resistance and Resistivity
Statement: Find the resistivity of 10 m long tungsten rod having area 4*10-6 m2
Tungsten resistivity: 5.485 X 10-8 Ω-m
From fromula ρ = A.R / l
R = ρl/A = (5.485 X 10-8 Ω-m * 10 m) / 4*10-6 m2