Resistivity Formula Unit, Chart, and Calculations with Solved Examples

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

  1. The resistivity material is dependent on the impurities within the materials
  2. 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

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