PhysicsChapter 7: Current Electricity
Length and Area
Introduction
The resistance of a uniform wire depends on its dimensions. For a wire: R = ρL/A where: `R` = resistance; `ρ` = resistivity of the material; `L` = length; `A` = cross-sectional area.
Definition
Effect of Length
**R ∝ L A longer wire has greater resistance because charge carriers experience more interactions while moving through the longer path. If length doubles: R doubles**, provided other factors stay constant.
Effect of Area
**R ∝ 1A A thicker wire has lower resistance because it provides more conducting cross-sectional area. If area doubles: R halves**, for the same material and length.
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Review the key facts, formulas and checks before you move on.Length and Area
Sticky Notes · Quick Revision
LONGER
- More R
THICKER
- Less R
R=ρL/A
- R=ρL/A