Electricity & Magnetism
Resistance
Resistance of a wire depends on geometry and material.
Variables
RΩ
Resistance
Electrical resistance
ρΩ·m
Resistivity
Material property
Lm
Length
Wire length
Am²
Cross-sectional area
Wire area
Derivation
R = ρL/A from microscopic Ohm's law.
Your notes
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Common questions
What is the Resistance formula?
Resistance is written R = ρL/A. Resistance of a wire depends on geometry and material. It belongs to Electricity & Magnetism, under Electric Circuits.
What are the units in R = ρL/A?
In SI units, R is resistance, measured in kg·m²/(A²·s³); ρ is resistivity, measured in kg·m³/(A²·s³); L is length, measured in m; A is cross-sectional area, measured in m².
How is the Resistance formula derived?
R = ρL/A from microscopic Ohm's law. The result is R = ρL/A.