Monday, February 28, 2011

Derive an expression for current in terms of drift velocity. (Derive I = nAev)

(This is being posted as per request from students)

Consider a conductor of length l and area of cross section A. Let the number of free electrons per unit volume be n. When a pd V is applied, let the drift velocity of electrons be v.

The total no. of free electrons in the piece of conductor = nAl (no. of free electrons per unit volume x volume)

Total charge due to free electrons; q  = nAle

The time taken by this charge to completely traverse the conductor, t =l/v

Therefore, the current in the conductor, I=q/t = nAle/(l/v) = nAev

i.e; I=nAev


1 comment:

  1. Paper is very lengthy. Hence no time for revision.
    some of the questions are unexpexted.
    Left dissatisfaction to the brilliant and hard working students since they lost centum in physics.


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