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Homework Help: Electric field inside an infinitely long cylinder.

  1. Apr 2, 2015 #1
    1. Prove, without using Gauss's law, that the field inside an infinitely long, uniformly charged cylinder is zero.

    2. Electric field of a charged surface

    3. My lead is that from a given point, I draw a very narrow cone to any piece of area on the cylinder, with distance r away.. That creates a piece of area dA, and assuming the charge density is σ0, that piece of area is inducting a field given by E = k*σ0*dA / r^2.

    Now I've tried to continue the line to the other end, but couldn't manage to come up with anything that would cancel the field..

    Any help?
  2. jcsd
  3. Apr 2, 2015 #2


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    Science Advisor

    If your point is not on the axis of the cylinder, your cone will have two different distances to the cylinder and cover two different areas.
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