1. If I put no excess charge on the conductor, the net charge on its inner surface will be: a] 0 b] +Q c] -Q d] -2Q e] cannot determine

2. Because there is zero E field in a conductor, the inner surface must hold a charge -Q. What is the charge on the outer surface? a] 0 b] +Q c] -Q d] -2Q e] cannot determine

3. With no net charge on the outer conductor, the inner surface gets -Q and so the outer surface gets +Q. Suppose, instead, I put +8Q on the outer conductor. What then is the charge on its inner surface? a] 0 b] +Q c] -Q d] +3Q e] +4Q

4. There still must be no field in the conductor. So the inner surface is still -Q. Thus, the outer surface will have +9Q, so that the total is 8Q (=+9Q - 1Q). Given the peanut shaped geometry and the fact that the charge +Q is off-center, is the charge density on the inner surface uniform (the same everywhere on that surface)? a] yes b] no

5. The negative charge on the inner surface will be concentrated close to the positive charge. (The E field next to the surface is stronger there !) If there is +9Q of charge on the outer surface, will the charge density on the outer surface be uniform? a] yes b] no

6. There is no electric field in the conductor. So the outside of the conductor cannot “know” that there is an off-center charge in the middle! So the charge density on the outer surface is uniform. a] yes

7. A metal box with no net charge is placed in an initially uniform E field, as shown. What is the total charge on the inner surface ? Assume this surface has area A. Answer A: 0 A] 0 B] C] D] E] cannot determine

8. No charge on the inner surface. What is the total charge on the outer surface? Answer A: 0 A] 0 B] C] D] E] cannot determine

9. No charge on the inner surface. Since the total charge is 0, there can be no net charge on the outer surface. What is the charge density on the left outer face of the box? Assume the external field is uniform, as shown.Answer: C A] 0 B] C] D] E] cannot determine

10. A point charge +Q is a distance d above an insulating sheet with charge density . What is the field at point P? Answer B

11. Insulating sheet: superposition of fields gives answer B. Suppose, instead, that a conducting sheet with charge density =  is brought from far away (far down, in the picture) to a distance d away from the charge +Q, then what is the field at P? Answer D

12. With a conducting sheet, the charge +Q will cause the charges to redistribute. Cannot determine! (Need Physics 400) Suppose, instead, that a conducting sheet with charge density = 0 is brought from far away (far down, in the picture) to a distance d away from the charge +Q, then what is the field at P? Answer: STILL D