# Resistivity, linear function of T

## Presentation

This model defines a resistivity **ρ** as a linear function of the temperature for an
isotropic or anisotropic material.

## Mathematical model

Resistivity is a linear function of the temperature.

The corresponding mathematical formula is written:

ρ (T)= ρ_{a}(1+a(T - T_{0}))

where:

- T
_{0}is the reference temperature [degree] - ρ
_{a}is the resistivity of the material at T_{0}[Ω .m] - a is a coefficient (positive or negative) [degree
^{-1}]

The shape of ρ(T) curve is presented in the figure below.

## Anisotropic material

For an anisotropic material, this linear model consists of a group of three straight lines.