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I Electric field inside a conducting wire

  1. Oct 20, 2016 #1
    The electric field in a 2.5mm×2.5mm square aluminum wire is 2.1×10−2 V/m . What is the current in the wire?
    The answer is I=4.65A.

    But my question is according to Gauss law, the electric field inside the conductor is zero. then how come this question says
    "The electric field in a 2.5mm×2.5mm square aluminum wire is 2.1×10−2 V/m "
  2. jcsd
  3. Oct 20, 2016 #2


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    Homework Helper
    Gold Member

    This is true only in electrostatic equilibrium. When you connect a voltage source across a conductor, there will be a non-zero electric field inside the conductor and it will drive a current through the conductor such that current density J=σ*E, where σ is the conductivity of the material.
    Last edited: Oct 20, 2016
  4. Oct 20, 2016 #3


    Staff: Mentor

    The response from @cnh1995 is correct, but may have left you wondering if Gauss law is violated. It is not. Gauss's law tells us that if there is no charge inside a surface then the net flux is 0. Inside a conducting wire there is flux, but there is just as much flux going in and going out, so the net flux is zero. Gauss's law holds.
  5. Oct 21, 2016 #4
    Thanks a lot for clearing my confusion.
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