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Electron drift speed in a copper wire.

by Alpha Russ Omega
Tags: copper, drift, electron, speed, wire
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Alpha Russ Omega
Apr8-07, 04:41 PM
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P: 30
I'm really stuck on this one problem:

"A small but measurable current of 4.20E-10 A exists in a copper wire whose diameter is 0.02 cm. Calculate the electron drift speed (in meters/second)."
Source: Serway and Jewett

I know that:
I = 4.20E-10 A
n = 8960 kg/m^3
q = 1.6E-19 C
d = 2E-4 m

J = (I/A) = n x q x v
Thus, v = I/(n x q x A)

What does A stand for and how would I go about finding it? Also, am I converting things correctly and using the proper value for the density?

Any help would be greatly appreciated.
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Apr8-07, 04:48 PM
P: 37
A is the cross-sectional area of the wire.
Alpha Russ Omega
Apr8-07, 05:15 PM
Alpha Russ Omega's Avatar
P: 30
Thank you for the hint. I found the answer now. Apparently I was getting the n density the wrong way as well.

Proper way to find n:

For the copper wire in the problem:

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