Find the electric field just inside the paint layer, outside,and surface. (HELP/CHECK WORK. I ALWAYS AWARD)?

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A charged paint is spread in a very thin uniform layer over the surface of a plastic sphere of diameter 15.0 cm , giving it a charge of -20.0 μC .

Part A

Find the electric field just inside the paint layer.

Part B

Find the electric field just outside the paint layer.

Part C

Find the electric field 6.50 cm outside the surface of the paint layer.

A)

EA=Q/Eo= 0 <<<<<<<<

———————————————————————

B)

Q= -20.0 μC

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EA=Q/Eo

E x 4pi(0.075^2)=(20.0×10^-6)/(8.854×10^-12)

E=3.196×10^7 <<<<<<<<<<

————————————————-

C)

4pi(0.075+0.065)^2

4pi(0.15)^2

E x 4pi(0.14^2)=(20.0×10^-6) / (8.854×10^-12)

E=5.56×10^5 <<<<<<<<<

• A) Exactly — flux = E*A = Q / εo

But the “enclosed charge” Q “just under the paint layer” is 0, so

the field E = 0 N/C (everywhere inside the paint layer).

B) This one looks set up fine. I’d round the result to 3.20e7 N/C.

C) Set up OK, but you erred in the first step — you should have

4pi(0.15)^2

Oh, wait; I see you’ve corrected that in the actual calculation.

But I still think you’ve made a calculator error somewhere.

I get 9.17e6 N/C.

Hope this helps!