Electron drift speed in a copper wire.

  1. 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.
  2. jcsd
  3. A is the cross-sectional area of the wire.
  4. 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: :smile:

    For the copper wire in the problem:
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