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Electric Field of a hollow conducting spherical shell

  1. Oct 23, 2013 #1
    1. The problem statement, all variables and given/known data
    A hollow conducting spherical shell has radii of .80m and 1.20m. The sphere carries a net charge of -500 nC. A stationary point charge of +300 nC is present at the center origin. Calculate the electric field at points:
    a) 0.30m
    b) 1.00m
    c) 1.50m

    I have attached the image as a document. because I didn't know how to paste it directly to the thread. Sorry for any inconvenience this may cause.


    2. Relevant equations
    E = (kq)/r^2


    3. The attempt at a solution
    I am able to solve the questions asked with ease. My only doubt is whether or not the .30m is E=0 because of its location within the hollow space of the conducting sphere.
     

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    Last edited: Oct 23, 2013
  2. jcsd
  3. Oct 23, 2013 #2

    haruspex

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    Will the charge on the shell be radially symmetric? If so, what field will that charge create inside the shell cavity?
     
  4. Oct 23, 2013 #3
    My answer to your question is yes, the problem states that it is a conducting sphere which tells me that the because there is a + charge at center then the inner wall of the conductor has a - charges due to polarization. But this also causes a bit of confusion for me because if the net charge is negative then by definition its excess charge is on the surface.
     
  5. Oct 23, 2013 #4
    in the hollow the radial charge is radially outward toward the (-) charges that are on the inner wall of the conducting sphere.
    At the second layer, the conducting sphere's solid area, the charge is radially inward due to the charge polarization and the + charges that are along the outer-most wall of the conducting sphere.
    Lastly, the outer edge of the conducting sphere has - charges on its outer surface, but this is where I am second guessing because it seems to me that those charges are too close to the + charges that are on the inner wall of the outer-most wall of the conducting sphere.
     
  6. Oct 23, 2013 #5
    but E = 0 inside the conductor. That I am certain of and there is definitely an E field outside the entire sphere.

    Thanks in advance for helping.
     
  7. Oct 24, 2013 #6

    haruspex

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    It certainly would be zero if there were no isolated charge. Or are you saying that the shell generates no field inside itself, despite the isolated charge?
    You've agreed that the charge on the shell is spherically symmetric. So consider a thin shell of it at some radius. The charge is uniform on that shell. What field will that generate inside itself?
     
  8. Oct 24, 2013 #7

    rude man

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    Think Gauss' law.
     
  9. Oct 24, 2013 #8

    rude man

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    What does Gauss' law tell you it is?
    Hint: it's not E = 0.
     
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