PHYSICS · Multi-part · CBSE · Physics · Electric Charges and Fields · Electric Charges and Fields
Problem
Three identical conducting pith balls, A, B, and C, hang from insulating threads so that they can move freely and are initially well separated. Their initial charges are qA=+4.0μC, qB=−1.0μC, and qC=+2.0μC. During a classroom demonstration the instructor carries out the following rapid sequence without allowing the balls to touch anything else:
1. Balls A and B are briefly allowed to touch and then separated.
2. Without delay, ball B is touched to ball C and then separated.
3. Finally, ball A is touched to ball C and all three balls are again separated far apart.
Assume charges redistribute uniformly upon any contact and no charge leaks to the environment.
(a) Construct a complete table showing the charge on each ball after each of the three numbered contacts.
(b) Verify quantitatively that electric charge is conserved for the three-ball system throughout the demonstration.
(c) Suppose that, contrary to the assumption, 1.5% of the total charge present just before the first contact were to leak to the humid air during each touching event. Recalculate the charges that would be measured on each ball at the end of step 3 under this new assumption.
(d) Discuss how an experimentalist could distinguish, using only charge measurements on the balls, between true charge leakage and a failure to achieve complete redistribution of charge during contact.