Matthiessen's rule, relating it to applied electric field

[rwooduk]

Homework Statement

Homework Equations

None.

The Attempt at a Solution

I understand the basic concept of Matthiessen's rule that the contribution to electronic resistivity / conductivity is split into two independant componants, resistivity due to impurities and resistivity due to the lattice. But I am unsure how this relates to if an electric field is applied. Also we have been taught it only applies if independant from the wavevector, could someone perhaps emphasise this a little?

Please could someone give me a point in the right direction.

 

[rwooduk]

Anyone?

The only thing I can think is that if the resistivity is proportional to the electric field then it somehow changes the wavevector so it cannot be used.