Consider a solid nonconducting sphere with a uniform

Question

charge density of ρ and a charge of -q, inside a
conducting spherical shell which has a charge of -q.
Suppose that R1=5 cm, R2=15
cm and R3=30 cm. Furthermore, suppose that q=3 nC.
Find the charge density on the outer surface of the
shell. (Take Coulomb's constant k=8.99x10 9 N m2
/C2
and π = 3.14).

Answer 1

total charge seen from outside outer shell = -2q
spread that over the surface area of 4 pi r^2