1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Homework Help: Quick Help!

  1. Feb 7, 2005 #1
    A metallic wire has a diameter of 4.12 mm. When the current in the wire is 8 A, the drift velocity is 5.4*10^-5 m/s.

    What is the density of free electrons in the metal?

    I have considered a wire of cross-sectional area A, with current I. V is the drift velocity of the free charges in the conductor and n is the number of charged particles per unit volume. Then the current is given by I = nqva, where q is the magnitude of the charge on a charge carrier.

    I = 8
    n = density??
    A = (2.06)^2 * 3.14
    v = 5.4 x 10^-5
    q = ??

    Can someone help me out on the answer for this problem? Thanks!
     
  2. jcsd
  3. Feb 7, 2005 #2

    dextercioby

    User Avatar
    Science Advisor
    Homework Helper

    Pay attention with the units... :grumpy:
    HINT:
    [tex] |\vec{j}|=\frac{I}{S}= n |q_{el.}| |\vec{v}_{drift}| [/tex]


    Daniel.
     
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook