Number of conduction electrons question

[raintrek]

Homework Statement

Calculate how many conduction electrons pass through a given area per second when a current of 1A flows.

Homework Equations

Current density, j = i/A (i=current, A=cross sectional area)
Current desntiy, j = nevD (n=no of electrons per unit volume, e=charge on electron, vD=drift velocity)

The Attempt at a Solution

I've taken an element of volume of length vDt and cross-sect area, A. I've surmised then that the total number of electrons in that area will be N=nAvDt.

All of those electrons will then cross a plane in 1 second, so I've equated j=i/A=nevD, and substituted n from the earlier (bold) equation - n=N/AvD. However, that produces a result of N=i/e=1/e ... doesn't look right! Help!

 

[antonantal]

However, that produces a result of N=i/e=1/e ... doesn't look right! Help!

That looks right to me. How do you think it should look like?

 

[AlephZero]

Look at it a different way, forget about the current density etc.

1A = 1 coulomb/sec

If the charge on one electron is e coulombs, then one coulomb is the charge on 1/e electrons.