# Homework Help: A dielectric in side a spherical shell

1. Dec 4, 2008

### FourierX

Assume that there is a spherical dielectric inside spherical shell. There is a vacuum between the dielectric and the shell.

I found this configuration rather tricky. Any idea ?

[URL=http://img117.imageshack.us/my.php?image=conductorly3.jpg][PLAIN]http://img117.imageshack.us/img117/5901/conductorly3.th.jpg[/URL][/PLAIN]

http://img117.imageshack.us/img117/7413/conductorwf9.jpg [Broken]

Last edited by a moderator: May 3, 2017
2. Dec 4, 2008

### m.e.t.a.

I'm not clear on your specific question. Could you elaborate?

3. Dec 4, 2008

### FourierX

Consider the diagram above. Assume that the didelectric in the middle of shell contains charge Q. With this fact, how should the electric field be determined ?

4. Dec 4, 2008

### Defennder

Why is this tricky? What can you say about the E-field from Gauss law?

5. Dec 5, 2008

### m.e.t.a.

FourierX, there are a few "rules" that, if you are aware of them, will enable you to solve your problem:

• The electric field outside of a uniformly charged sphere is the same as if all the charge were concentrated at its centre-point. This is true whether the sphere is hollow, solid, conductive or dielectric. This is also true of a hollow conductive shell which contains within its cavity any static arrangement of charges.
• The electric field inside a hollow conductive shell is zero.
• The electric field inside the body of a conductor is zero.

I would suggest that you have a try at deriving the above rules yourself. The maths is not difficult and your understanding will increase in the process. Best of luck.