# Sphere of charge

1. Feb 10, 2006

### psingh

A sphere of radius R has total charge Q. the volume chrage density within the sphere is

p=p_0(1-r/R)
the charge density decreases linearly from p_0 at the center to zero at the edge of the sphere.

1) show that p_0= 3Q/pi*R^3

to find this i used p*volume=Q
Q/volume=p

p_0(1-r/R)=Q/volume and the volume of a sphere is 4/3pi*r^3

is this right??

2. Feb 10, 2006

### Staff: Mentor

Q = the volume integral of the charge density over the volume of the sphere.

Q = $\int_V\,\rho(r)\,dV$. One needs to find the expression for dV in spherical coordinates, and since the distribution is dependent only one r, the integral can be simplified with respect to the polar and azimuthal angles.

Last edited: Feb 10, 2006