An end of chapter question that i dont really know how to do..(adsbygoogle = window.adsbygoogle || []).push({});

Question:

A copper connecting wire has a cross-sectional area of 3mm^2 and is 30cm long. (A) Estimate the amount of free charge in this wire. (B) How long will it take for all this free charge to pass through the wire when a current of 3 A flows? (C) Hence find the average speed at which this free charge moves.

Well i know the formula i have to use is; I=naqv where

I = Current

N = Charge carrier density

Q = Charge

V = Drift velocity.

It tells me in the chapter that the atoms of copper have a diameter of 0.25 nm

I need to work out the amount of atoms in a volume of (3mm^2 x 30cm) which equals: 3mm^2 x 300mm = 900mm^3 . = 0.9 m

so now to work out the number of atoms its 0.9 / .25nm = 3.6 x 10^9

then cube that = 4.6656 x 10^28 atoms per 0.9m cubed

actually i dont think ill go further just yet, but are things looking good upto this point??

Help REALLY! appreciated

Regards,

Mo

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# Homework Help: Charge carrier density i=navq

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