Induction

Two metal spheres that are initially uncharged are mounted on insulating stands, as shown above. A negatively charged rubber rod is brought close to, but does not make contact with, sphere X. Sphere Y is then brought close to X on the side opposite to the rubber rod. Y is allowed to touch X and then is removed some distance away. The rubber rod is then moved far away from X and Y. What are the final charges on the spheres?

• Sphere X Sphere Y

  A) Zero Zero

• Sphere X Sphere Y

  B) Negative Negative

• Sphere X Sphere Y

  C) Negative Positive

• Sphere X Sphere Y

  D) Positive Negative

• Sphere X Sphere Y

  E) Positive Positive

Two initially uncharged conductors, 1 and 2, are mounted on insulating stands and are in contact, as shown above. A negatively charged rod is brought near but does not touch them. With the rod held in place, conductor 2 is moved to the right by pushing its stand, so that the conductors are separated. Which of the following is now true of conductor 2?

• (A) It is uncharged.

• (B) It is positively charged.

• (C) It is negatively charged.

• (D) It is charged, but its sign cannot be predicted.

• (E) It is at the same potential that it was before the charged rod was brought near.

A charged rod is placed between two insulated conducting spheres as shown. The spheres have no net charge. Region II has the same polarity as Region

• (A) I only

• (B) III only

• (C) IV only

• (D) I & III only

• (E) I & IV only

• a

• b

• c

• d

• e