# Resistivity, exponential function of T

## Presentation

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

## Mathematical model

The resistivity is an exponential function of the temperature.

The corresponding mathematical formula is written:

where:

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

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

## Anisotropic material

For an anisotropic material, the exponential model consists of a group of three exponentials.