A thin insulating rod with charge density +5nC/m is arranged inside a thin conducting cylindrical shell of radius R=3cm. The rod and shell are on the same axis, and you can assume they are both infinite in length. What is the surface charge density induced on the outside of the conducting shell in nC/m^2?

Question

I thought since the rod and shell is infinite in length the electric field is zero inside. Therefore, the charge density on the outside of the conducting shell is - -5nC/m. That seemed too easy.

Then my next answer was
charge density(outer) =
-(lambda/2*pi*r)= - (5/(2*pi*0.03) = -26.5258 nC/m^2

I have no other solutions.

Thank you.

Answer 1

Only it says on the outside of the conducting shell. Be sure to check the positive/negative signs in your answer.