# How they got formula 1.7 from formula 1.6

there is no rho in 1.6
and E dissapeared

??

Borek
Mentor
I have not the slightest idea what it is all about, but perhaps σρ=1.

its about solid state physics and semiconductors
and there is no rho in 1.6

What work have you done so far to find how σ and ρ are related?

You obviously have gaps in the subject and should review EM before continuing on. It's such a simple relationship.

$$\sigma =\frac{ne^2\tau }{m}$$

$$E =\rho J$$

$$\tau=\frac{m}{\rho n e^2}$$

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here is a hint.

What is definition of σ?

What is definition of ρ?

can you find this out please.

thanks :)