PLEASE READ THE WHOLE PROBLEM a charged paint is spread in a very thin uniform l

Question

PLEASE READ THE WHOLE PROBLEM

a charged paint is spread in a very thin uniform layer over the surface of a plastic sphere of diameter 12 cm giving it a charge of -35 microcoulombs find the electric field:

a) just inside the paint layer

b) just just outside the paint layer

c) 5 cm outside the surface of the paint layer

The answers are E=0, E=-8.75x107, and E=-2.6x107 respectively. I need help not on the answers but the conceptual aspects.

Why does E=0 inside the plastic sphere when plastic is an insulater and thus the charged paint would induce a charge, right? I thought E=0 was for conductors where the charge induced would rush to the surface leaving no E inside of the volume

Explanation / Answer

(a)

Inside the sphere, there is no charge, so, there is no electric field.

            E = 0 N/C

(b)

The electric field is,

            E = kq/r^2

               = (9x109)(35x10-6)/(0.12/2)2

                = 8.75 × 10^7 N/C

(c)

The electric field is,

E = kq/r^2

    = 9x109)(35x10-6)/(1.1)2

  = 2.60 × 10^7 N/C

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