# Tensor Equations for Anisotropic Materials

1. Apr 4, 2013

### KayDee01

Hi,
I am in the middle of revising for and a classical electromagnetism exam, and I've hit a wall when it comes to tensor equations.

I know that for anisotropic materials: $J=σE$ and $E=ρJ$
And that in component form the first equation can be written as $J_i = σ_{ij} E_j$

My question is, does $J_i=σ_{ii}E_i$ make mathematical sense and if so does it make physical sense when applied to anisotropic materials. The second part of my question is, if this does make sense, is the final value of $J_i$ written as: $J_i=σ_{ij} E_j+σ_{ii}E_i$ or is there another way to combine the two values of $J_i$?