Electric behavior of materials: definitions
Definition
The macroscopic dependence linking the values of the electric current density J and the electric field strength E in any point of material is called the law of material electric behavior.
This law 
represents the
local formulation of Ohm's law.
Notation
This law is written in the form:
or 
where:
- σ is the conductivity tensor
- ρ is the resistivity tensor
The electric conductivity σ is a measure of how well a material allows electric current flow. ( It stands for the capacity of the material that contains movable electric charges to make them flow under the action of the electric field.)
The electric resistivity ρ is a measure of how strongly a material opposes the current flowing.