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Design issues


Observations of how the resistance varies with size of a sample suggest that resitivity obeys the relationship:
Electrical resistivity = resistance * cross-sectional area / length

The resistivity can therefore be calculated quite easily be measuring the resistance of a piece of wire of constant cross-section and known length.

In practive resistivity is difficult to measure accurately because of the effect of temperature. More sophisticated techniques need to be used if accurate measurements are required, e.g. a Wheatstone bridge.

Units & Values

From the definition of resitivity it can be seen that it has units of ohm-metres. Giving exact values can be difficult because of the strong temperature dependence. Data are usually given for room temperature.