Resistivity

In the previous lesson, you saw that the resistance of a wire depends on its length, cross-sectional area, and the material it is made from. Resistivity is the property that captures the material's inherent ability to resist the flow of current, independent of the wire's dimensions.

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Defining Resistivity

The resistance of a uniform conductor is given by:

R = ρL / A

where:

• R = resistance in ohms (Ω)
• ρ = resistivity of the material in ohm metres (Ω m)
• L = length of the conductor in metres (m)
• A = cross-sectional area in square metres (m²)

Rearranging for resistivity:

ρ = RA / L

Resistivity is a property of the material itself — it does not depend on the shape or size of the sample. A copper wire 1 m long has the same resistivity as a copper wire 10 m long, even though their resistances differ.

Typical Resistivity Values