A negative charge - Q is placed inside the cavity of a hollow metal solid. The outside of the solid is grounded by connecting a conducting wire between it and the earth.
(a) Is there any excess charge induced on the inner surface of the piece of metal? If so, find its sign and magnitude.
(b) Is there any excess charge on the outside of the piece of metal? Why or why not?
(c) Is there an electric field in the cavity? Explain.
(d) Is there an electric field within the metal? Why or why not? Is there an electric field outside the piece of metal? Explain why or why not.
(e) Would someone outside the solid measure an electric field due to the charge -Q? Is it reasonable to say that the grounded conductor has shielded the region from the effects of the charge -Q? In principle, could the same thing be done for gravity? Why or why not?