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Homework Help: Gauss's Law Problem

  1. Oct 24, 2006 #1
    A long straight conducting rod (or wire) carries a linear charge density of +2.0uC/m. This rod is totally enclosed within a thin cylindrical shell of radius R, which carries a linear charge density of -2.0uC/m.
    A) Construct a Gaussian cylindrical surface between the rod and the shell to derive then electric field in the inner space as a function of the distance from the center of the rod.
    B) Construct a Gaussian cylindrical surface outside both the rod and the shell to calculate the electric field outside the shell.

    This is what i have so far.

    E=q/4piEor^2
    E=+2.0uC/m / 4pi8.85x10^-12(-2uC/m)^2
    E=4.5x10^9Nm^2/C
     
  2. jcsd
  3. Oct 24, 2006 #2

    Andrew Mason

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    It asks you to apply Gauss' law:

    [tex]\oint E\cdot dA = \frac{Q_{encl}}{\epsilon_0}[/tex]

    If you pick a gaussian surface through which you know E is constant due to all points on the surface being equidistant from equal charges, the integral is simply

    [tex]E\cdot A = \frac{Q_{encl}}{\epsilon_0}[/tex]

    Pick a surface that is inside the cylinder that fits that description and do the calculation.

    AM
     
    Last edited: Oct 24, 2006
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