Question

9. A point charge Q = 1.00 × 10−6 C is located at the centre of a non-conducting spherical shell of radius rA = 0.500 m that has a surface charge density of ηA = 1.25 × 10−6 C m−2 . This spherical shell is itself concentric with a conducting shell of radius rB = 1.00 m which initially has the same surface charge density but with opposite sign, i.e., initially, its surface charge density ηB = −ηA. The outer shell is then grounded so that the electric field outside the outer shell is zero.

(a) Find the surface charge density on the outer shell after the shell has has been grounded. Provide a sketch of the initial and final charge distributions, and draw a few field lines (not too much detail is required here).

(b) How much energy is released when the outer shell is grounded?

Answer 1