Disclaimer: This is not a homework question. This came from an online resource that I've been using to tutor a student. After much thought, I found myself going in circles on this one.
- Two neutral conducting spheres, A and B, which are initially in contact, are brought close to a rod (positively charged). Sphere B is taken away. The investigation is repeated with a negatively charged rod, same procedure of steps. Which of the following is true?
(It's not clear to me, by the way, if they mean that we bring the rod close, remove sphere B, and then repeat the procedure with sphere B absent. Or just repeat the entire procedure, with sphere B present again.)
A. The rod induces charge separation, so sphere A gains a charge opposite that of the rod. Removing B, sphere A retains that charge and is therefore attracted to the rod in both cases.
I understand that the rod should induce a charge separation. But it's not clear to me how that relates to the fact that there are two spheres in contact. The problem makes no distinction regarding where, relative to the spheres, the rod is placed "close" by. So if we factor out relative location, then it seems like, due to lack of contact, all we should expect is a temporary charge separation. After which the sphere, being removed, wouldn't affect anything.
B. Charges from the rod transfer to sphere A, making them the same charge. There is repulsion between these two objects in both cases since they are like charges.
This answer doesn't make sense to me due to the fact that the rod doesn't come into direct contact with either sphere.
C. Because sphere A remains neutral throughout the experiment, it will attract any nearby charged object because of induced charge separation. So attraction in both cases
I ruled this out as close to nonsensical for awhile until I started to regard it as the most likely answer due to problems I had with the others. Currently it's my top contender.
D. The gravitational force between objects is always attractive, and at this scale the gravitational forces are more dominant than electric forces in both cases so attraction wins
Nonsensical answer of course.