What is Resistivity?
Specific electrical resistance or resistivity is a fundamental property of a material that measures how strongly it resists electric current. A low resistivity indicates a material that readily allows electric current. Resistivity is defined as the resistance offered by the material per unit length for unit cross-section and is inversely proportional to resistance.
We can also define the resistivity of any object as the ratio of the electric field, and the current density. The formula for the same is,
ρ = E/J
where,
- ρ is the resistivity of the material and is measured in Ω.m
- E is the electric field and is measured in V.m-1
- J is the current density and is measured in A.m-2
Units of Resistivity
- Resistivity is commonly represented by the Greek letter ρ (rho).
- SI unit of electrical resistivity is the Ohm-meter (Ω-m) or mho.
Relation between Resistance and Resistivity
Mathematically formula for resistivity or the relation between resistance and resistivity is given as follows:
ρ = (R×A)/L
R = (ρ×L)/A
Where,
- R is the Resistance,
- L is the Length and
- A is the cross-sectional area of the conductor.
Resistivity of Some Common Materials
Materials with a low value of resistivity conduct electricity very well are conductors and insulators will have a higher value of resistivity than that of conductors. Some materials and their standard specific resistance (Resistivity) at 20° C:
|
Material |
Resistivity (in Ω-m) |
|---|---|
| Aluminum |
2.8 × 10-8 |
| Copper |
1.7 × 10-8 |
| Gold |
2.4 × 10-8 |
| Carbon (Graphite) |
1 × 10-5 |
| Germanium |
4.6 × 10-1 |
| Iron |
1.0 × 10-7 |
| Lead |
1.9 × 10-7 |
| Nichrome |
1.1 × 10-6 |
| Silver |
1.6 × 10-8 |
Electrical Resistance
Electrical resistance is the obstruction offered by the material in the flowing of the current or charge through the material. Thus, the higher the resistance the lower the amount of current passing through it. It is the property of a material that tells us about the flow of the current through the material. The substances that easily conducts the electric current are called conductors and they have very low electrical resistance, on the contrary, the substance that does not easily conducts the electric current are called insulators and they have very high resistance.
In this article, we will learn about, electrical resistance, its formula, factors affecting electrical resistance, and others in detail.
Table of Content
- What is Electrical Resistance?
- Resistance Formula
- Factors Affecting Resistance
- Electrical Resistor Symbol
- What is Resistivity?
- Difference Between Resistance And Resistivity
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