Electric Field of a Dielectric Sphere

[Marvi]

Homework Statement

A uniform charge q is distributed along a sphere of radius R.
a) What is the Electric Potential in the center of the sphere?

Homework Equations

V(r1)-V(r0) = - \int \stackrel{\rightarrow}{E} * \stackrel{\rightarrow}{dl}

The Attempt at a Solution

 

[kuruman]

You will need to find the electric field both inside and outside the field and integrate the expression you posted from infinity to R using the field outside and then from R to zero using the field inside.

 

[Marvi]

Thanks for answering, but actually I can't find the expression for the second part of the Electric field

The first is inside the sphere which leads to \frac{Kq}{R} but the Electric field of the outside part of the sphere I don't know what to do

obs: the answer is : \frac{6kq}{R}

 

[kuruman]

Use Gauss's Law to find the field in the two regions.