# Electric field and gauss law for different models of sphere

1. Apr 17, 2013

### exuberant.me

Hello all!!! I actually have a few doubts regarding "gauss law" when applied "for different models of sphere"

First, If we place a charge 'Q' inside a spherical shell at the center (somehow) then it should come out to its surface that means in no way can we do it. True or False????

Next,

Considering a solid sphere having a charge Q uniformly distributed on its outer surface. Thus everywhere inside it is the electric field equal to 0.

But i have somewhere read that the electric field inside a solid sphere is Kqr/R^3.

Or is it that , there is a difference in these two statements
"A charge uniformly distributed on the surface of a solid sphere" and
"A symmetrical spherical distribution of charge" ????

Also, How can we get a spherical symmetrical distribution of charge?
. By placing the charge at the center of the solid sphere???? (which is again impossible i guess)

I'll be greatly thankful if someone clears these brain storming doubts?

2. Apr 17, 2013

### tiny-tim

hello exuberant.me!!!

(try using the X2 button just above the Reply box )
sorry, no idea what you mean
yes … Kqr/R3 is for a charge uniformly distributed throughout the volume (use gauss law! )
no, by chucking the charges in, and giving them a good old stir

like making a pudding

3. Apr 17, 2013

### Staff: Mentor

With no lumps, of course... nice and smooth...

4. Apr 17, 2013

### BruceW

mathematically,
$$\frac{\partial \rho}{\partial \theta} = \frac{\partial \rho}{\partial \phi} = 0$$
and practically how this could happen for a solid sphere with fixed charges? ...err... maybe in Neutron stars that have a surplus of electrons? The electrons wouldn't be fixed, but in equilibrium the charge distribution would be spherically symmetric... unless it was a pulsar?

So you just have to make a neutron star :) easy-peasy.