# How they got formula 1.7 from formula 1.6

1. Mar 20, 2010

### nhrock3

there is no rho in 1.6
and E dissapeared

??

2. Mar 20, 2010

### Staff: Mentor

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

3. Mar 20, 2010

### nhrock3

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

4. Mar 20, 2010

### waht

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.

5. Mar 20, 2010

### nhrock3

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

$$E =\rho J$$

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

Last edited: Mar 20, 2010
6. Mar 20, 2010

### waht

here is a hint.

What is definition of σ?

What is definition of ρ?

can you find this out please.

7. Mar 20, 2010

thanks :)