- #1

pesslovany

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Firstly I appologize, that I am not native english speaker and I don't study physics(but cybernetics we are getting just some general knowledge about physics), but hopeffuly I will write this right.

We know that inside of a conductive object is protected from influence of outside electrical charges.

a. Analogically, is outside of the conductive object protected from influence of inside electrical charges? For example from point charge Q situated inside the hollow sphere at a random spot.

b. The point charge is directly in the middle of the cavity of hollow sphere. Consider what is specific about this setup.

a. If I place a point charge Q+ inside the sphere, then because the sphere is conductive( therefore has free electrons ), the electrons will move to the inside of the shell to "cancel" electric field from inside charge. This will leave the outside surface of the shell positively charged, therefore creating electromagnetic field on the outside. Meaning outside of the shell is not protected from the inside charge. That is what I came with, but I am supposed to proof this by some equation, I don't really know where to start here...

b.I guess - by the picture - I am supposed to express E. I can divide this problem into three parts: inside the cavity of the shell, outside the shell and in the shell object itself.

## Homework Statement

We know that inside of a conductive object is protected from influence of outside electrical charges.

**2. Questions**a. Analogically, is outside of the conductive object protected from influence of inside electrical charges? For example from point charge Q situated inside the hollow sphere at a random spot.

b. The point charge is directly in the middle of the cavity of hollow sphere. Consider what is specific about this setup.

## The Attempt at a Solution

a. If I place a point charge Q+ inside the sphere, then because the sphere is conductive( therefore has free electrons ), the electrons will move to the inside of the shell to "cancel" electric field from inside charge. This will leave the outside surface of the shell positively charged, therefore creating electromagnetic field on the outside. Meaning outside of the shell is not protected from the inside charge. That is what I came with, but I am supposed to proof this by some equation, I don't really know where to start here...

b.I guess - by the picture - I am supposed to express E. I can divide this problem into three parts: inside the cavity of the shell, outside the shell and in the shell object itself.

1. Inside cavity: For inside cavity I used standard Gauss law therefore i got :

[tex]E = \frac{1}{4\pi\epsilon}\cdot\frac{Q}{r^2}[/tex]

2. In the shell: Here the E should be 0 after electrons cancel the point charge and stop moving. Again I should proof this but I don't really know where to start.

3. Outside: I am not really sure here, but I guess it should be:

[tex]E = \frac{1}{4\pi\epsilon}\cdot\frac{Q}{(r-R_2)^2}[/tex]

So I would be very happy if you could help me with the two proofs and if you could check, if the rest of my thoughts are allright. Thank you in advance.

[tex]E = \frac{1}{4\pi\epsilon}\cdot\frac{Q}{r^2}[/tex]

2. In the shell: Here the E should be 0 after electrons cancel the point charge and stop moving. Again I should proof this but I don't really know where to start.

3. Outside: I am not really sure here, but I guess it should be:

[tex]E = \frac{1}{4\pi\epsilon}\cdot\frac{Q}{(r-R_2)^2}[/tex]

So I would be very happy if you could help me with the two proofs and if you could check, if the rest of my thoughts are allright. Thank you in advance.

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