Density definition(semiconductor nightmare 2)

  • Thread starter nhrock3
  • Start date
  • #1
415
0

Main Question or Discussion Point

2dlqko5.jpg

drude replaces V=RI with E=rho*j

current density is the amount of charges that crosses a certain area
in an amount of time.
but here they say that if current flows threw a wire of length L etc..
that the current density will be ..

but in the first definition of density there is no length of a wire aspect involved
??

so i cant understand how the length involved here if its not mentioned
in the first definition
 

Answers and Replies

  • #2
245
13
Maybe you should keep all your questions to one thread since they all seem to be about solid state physics. To answer your question here: if you multiply a density time a velocity you end up with flux (something/(area)).

list all the units just like we did in the other thread and you'll see. (I'll help you one more time with this.)

[tex]j = -nev[/tex]

[tex]j \frac{charge}{seconds}\frac{1}{cm^2}= -n \frac{electrons}{cm^3}e \frac{charge}{electrons}v \frac{cm}{seconds}[/tex]

FYI: Typically, when you work SS problems, you express velocities in (cm/s) not (meters/s). Be careful of unit conversions. Memorize conversions between meters to Angstroms and cm to Angstroms. Trust me on that.
 

Related Threads for: Density definition(semiconductor nightmare 2)

Replies
2
Views
1K
Replies
2
Views
1K
Replies
5
Views
1K
  • Last Post
Replies
1
Views
636
  • Last Post
Replies
1
Views
1K
  • Last Post
Replies
2
Views
982
Replies
2
Views
2K
  • Last Post
Replies
6
Views
2K
Top