Three identical metallic blocks—A, B, and C—are mounted on separate insulating stands and arranged in a straight line with equal center-to-center separations that are large compared with the size of the blocks. Initially, all three blocks are electrically neutral. A technician performs the following sequence without ever allowing the blocks to touch each other:
1. A positively charged rod is brought near block A and held fixed. While the rod is in place, block A is momentarily connected to ground and the ground connection is then removed.
2. The charged rod is taken away.
3. Block A is moved until it briefly touches block B, then it is returned to its original position.
4. Block C is now slid to a position halfway between blocks A and B and left there.
Assume the laboratory air is perfectly insulating so no charge leakage occurs at any time.
(a) For each block, indicate whether its net charge is positive, negative, or zero immediately after Step 2. Support each determination with a detailed explanation that cites relevant physical principles.
(b) After Step 3, determine the net charge on blocks A and B. Clearly outline the reasoning path you use to reach your conclusion.
(c) Rank the magnitudes of the electrostatic forces experienced by block C due to blocks A and B after Step 4. Provide a complete justification that references charge magnitudes and separation distances.
(d) The technician claims that throughout the entire experiment the algebraic sum of the net charges on the three-block system remained constant. Construct an argument evaluating this claim, explicitly identifying each stage at which charge transfer did or did not occur.