A hollow sphere has a uniform volume charge density of 2.22 nC/m3. The inner radius is a = 12.2 cm and the outer radius is b = 24.4 cm.

Question

What is the magnitude of the electric field at 18.3 cm from the center of the sphere?

What is the magnitude of the electric field at 78.1 cm from the center of the sphere?

Answer 1

Shells can be treated as point charges so this question simplifies considerably. E = kQ/r^2.
To find Q multiply the charge density times the volume. Which by the way is a bit silly because all the charge is on the shell. Whatever.
2.22 * 4/3 pi r^3. You can even make it easier just jumping to E = k *2.22 * 4/3* pi *r. Are you sure there wasn't a charge on the outer shell? It would make things harder

Answer 2

45h