Assuming that the rod's total charge dominates any induction, what happens to end A as a negatively charged ball approaches it after many prior contacts?

• A. It is repelled.
• B. It is attracted.
• C. It remains neutral.
• D. It rotates.

Answer: (A)

The situation tests how net charge dominates over induction in electrostatics. The ball is negatively charged, and after many contacts the rod has a net negative charge. While a nearby neutral conductor would polarize and have a temporary positive region near the approaching charge (which could cause attraction), the rod’s overall negative charge overrides that effect. The near end of the rod carries excess negative charge, so like charges repel each other. As the negatively charged ball approaches, repulsion pushes the rod’s near end away and the ball away as well. That’s why the end is repelled.