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Homework Help: Calculating Flux for Hemispheres of Different Radii

  1. Feb 7, 2009 #1
    1. The problem statement, all variables and given/known data

    For some reason, I'm not quite understanding this scenario.


    Two hemispherical surfaces, 1 and 2, of respective radii r1 and r2, are centered at a point charge and are facing each other so that their edges define an annular ring (surface 3), as shown. The field at position [tex]\vec{r}[/tex] due to the point charge is:

    [tex]\vec{E}[/tex]([tex]\vec{r}[/tex])= [C/(r^2)]*[tex]\hat{r}[/tex]

    where C is a constant proportional to the charge, r=|[tex]\vec{r}[/tex]|, and [tex]\hat{r}[/tex]=[tex]\vec{r}[/tex]/r is the unit vector in the radial direction. "

    I'm supposed to find electric flux through the three different surfaces, but for some reason, this picture just doesn't make sense to me.

    2. Relevant equations

    Electric flux is the integral of the dot product of electric field and dA (differential area element).

    3. The attempt at a solution

    I want to try figuring it out on my own first before I ask for help, but I don't quite understand this scenario. For example, I don't understand how the two images provided correlate, and I don't understand what the three different surfaces are. Sorry if the answer to this is obvious. ><
  2. jcsd
  3. Feb 7, 2009 #2
    See attached file

    Attached Files:

  4. Feb 7, 2009 #3
    How do I open it?
  5. Feb 8, 2009 #4
    You don't need to open it. It's just an image to help you understand the surfaces.
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