a) A lightning rod is a rounded copper rod mounted on top of a building and welded to a heavy copper cable running down into the ground. Lightning rods are used to protect houses and barnes from lightning; the lightning current runs through the copper rather than through the building. Why. Why should the end of the rod be rounded?

b) A solid conductor has a cavity in its interior. Would the presence of a point charge inside the cavity affect the electric field outside the conductor.Why or why not? Would the presence of a point charge outside the conductor affect the electric field inside the cavity? Again, why or why not

c) Explain this statement? ''in a static situation, the electric field at the surface of a conductor can have no component parallel to the surface because this would violate the condition that the charges on the surface are at rest. '' would this same statement be valid for the electric field at the surface of an insulator? Explain why answer and the reason for any differences between the cases of a conductor and an insulator.