# Resistivity

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Besides temperature, experimental results shows that the resistance (R of a given conductor) also depends on the composition and size.

Resistance, R is found to be:

• directly proportional to its length, L
• inversely proportional to its cross-sectional area
• dependent on the type of material

From experimental results, we can show that:

$R = \rho \frac{L}{A}$

,where

R = resistance in ohm ($\Omega$)
A = cross-sectional area of conductor in metre2 (m2)
L = length of conductor in metre (m), and
$\rho$ = resistivity of material in ohm-metre ($\Omega m$)

For the similar lengths and material,
Thinner wires have higher resistance than thicker wires.

For similar thickness and material,
Longer wires have higher resistance than shorter wires.