A hollow non-conducting spherical shell has inner radius R1 = 8 cm and outer radius R2 = 15 cm. A charge Q = -35 nC lies at the center of the shell. The shell carries a spherically symmetric charge density ? = Ar for R1 < r < R2 that increases linearly with radius, where A = 21 ?C/m4.
a) Write an equation for the radial electric field in the region r < R1 in terms of Q, r, and Coulomb's constant k. You may take the positive direction as outward.
b) What is the radial electric field at the point r = 0.5R1? Given your answer in units of kN/C, and take the positive direction outwards.
c) What is the radial electric field at the point r = 0.5(R1+R2)? Give your answer in units of kN/C.
d) What is the radial electric field at the point r = 2R2? Give your answer in units of kN/C.