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**1. Homework Statement**

Ast stated above: Biut i just cant get the correct answer!

radius of sphere = a

charge ze contained

**2. Homework Equations**

by gauss: E= (ze)*r/4pi(epsilon)*a^3 at any point within the sphere.

and

dv=r^2*sin(theta)dTheta*dphi*dr

Energy density= 0.5*epsilon*E^2

**3. The Attempt at a Solution**

letting energy= integral(energy density)dv

with limits: r= 0-a, theta= 0-pi, phi=0- 2pi

i get wrong answer:

(ze)^2/80epsilon*pi*a ration between top and bottom, should be 3(ze)^2/20epsilon*pi*a any ideas?

many thanks!