# Choice and definition of the application

## Introduction

The first stage corresponds to the choice and the definition of the application.

The two applications are the applications Supplied conductors and Conductors impedance.

The user defines a material (by default).

## Reference frequency

In practice, the reference frequency is fixed via the scenario of the solving process. (see § Solving process (according to the scenario)).

The reference frequency is the maximum frequency of the scenario.

## Materials

The materials are electric conductive materials characterized by their resistivity in Ω.m.

Only unidirectional conductors of tube type and whose cross-section is rectangular or hollow can be made of a linear homogeneous and isotropic magnetic material characterized by its relative permeability.

The characteristics of available materials are presented in the table below.

Material Resistivity (20°C)
Aluminum ρAl = 2,74.10-8 Ω.m
Copper ρCu = 1,72.10-8 Ω.m
Gold ρAu = 2,21.10-8 Ω.m
Silver ρAg = 1,63.10-8 Ω.m

## Skin depth: definition

For a linear homogeneous and isotropic material the average value of “skin” depth, in which the electric currents flow, can be calculated using the following formula: where:

• f is the frequency
• ρ is the resistivity of the material
• μ0 is the permeability of vacuum; μ0 = 4 π 10-7 H/m
• μr is the relative permeability of the material