Resistivity

Resistivity is a property of materials that determines how well that material will conduct electricity. This property is closely related to resistance which is the property of a particular electrical component. Resistivity is also closely related to electrical conductivity:

$\rho =\frac{1}{\sigma }$

Where $\rho$ is the resistivity (in Ohm/m) and $\sigma$ is the conductivity (in m/Ohm)). To determine the resistance of a wire (which could be made of almost anything: copper, aluminum, this equation even works for wood!)

$R=\rho \frac{A}{l}=\frac{A}{\sigma l}$

where $A$ is the area (in m²) and $l$ is the length (in m).

For more detailed information on resistivity please see hyperphysics. Hyperphysics also has a table of resistivities for different materials. Resistivity also depends on temperature, which is also explained on hyperphysics.

PhET: Resistance in a wire

The University of Colorado has graciously allowed us to use the following Phet simulation. Explore the simulation to see how resistance changes depending on geometry and resistivity: