Re: [Phys-L] Charge division on Spheres.

[brian whatcott <betwys1@sbcglobal.net>]

Thanks to Carl, for  persevering with my charge-capacitance difficulty:

 I was not clear on the orientation of the container and cans, so I 
added two pictures.

Photos added 5/4/2017

Graph of Capacitance versus Diameter of equivalent Sphere.
http://s880.photobucket.com/user/betwys/media/Capacity%20of%20%20Right%20Cylinders/cap-quiv.jpg.html

Graph of Capacitance versus Surface Area of Can
http://s880.photobucket.com/user/betwys/media/Capacity%20of%20%20Right%20Cylinders/cap-surf.jpg.html

Here are the kitchen table experimental materials:

Photo of cans , pot and cover
http://s880.photobucket.com/user/betwys/media/Capacity%20of%20%20Right%20Cylinders/IMG_1932.jpg.html

Photo of largest can in place before connections and lid placement
http://s880.photobucket.com/user/betwys/media/Capacity%20of%20%20Right%20Cylinders/IMG_1933.jpg.html

Brian W


On 5/4/2017 3:36 PM, Carl Mungan wrote:
> I’m not sure I exactly understand the geometry of how the can sits inside the steel container (a sketch would help), but if they are concentric we might model them as a cylindrical capacitor so that:
>
> C = 2 pi epsilon0 LENGTH / ln(0.23/DIAM)
>
> This gives a result that is in relatively good linear agreement with your measured values except it is too small by a factor of 2. We might try to improve it by adding the two end caps (assuming the cap is closed all around) in parallel modeled as parallel-plate capacitors:
>
> C = 2 pi epsilon0 LENGTH / ln(0.23/DIAM) + pi epsilon0 DIAM^2 / d
>
> where d = length of steel container - LENGTH. It can’t be that length of steel container = 0.132 m because that is smaller than your biggest LENGTH value. So I probably have the geometry wrong.
>
> Anyhow, you might improve on what I’ve done or make the geometry more nearly concentric cylinders. -Carl
>
>
>
>
> On 5/2/2017 8:41 PM, Carl Mungan wrote:
> > > For an isolated sphere, C = R/k. /snip/  -Carl