Question

Five balls, numbered 1 to 5, are suspended using separate threads. Pairs (1, 2), (2, 4), (4, 1)
show electrostatic attraction, while pairs (2, 3) and (4, 5) show repulsion, therefore ball 1 must be:

• A. Positively charged
• B. Negatively charged
• C. Neutral
• D. Made of metal

Answer 1

Answer: (C)

It should be neutral because $2$, and $4$ show attraction means have opposite charge $2$ too show attraction with $1$ means $1$ and $4$ should have same charge but as they are showing attraction too then. $1$ should be electricity neutral. Besides, it can be seen that ball $2$ is positively charged then ball $4$ is negatively charged because $2$ and $4$ show attraction. Now ball if ball $2$ is $(+ve)$ charged then ball $3$ is also $(+ve)$ charged because $2$ and $3$ also show repulsion and similarly ball $5$ is $(-ve)$ charged because ball $4$ and $5$ show repulsion and we left with ball $1$ and it never be $(+ve)$ by charged because ball $2$ and $1$ show attraction it means ball $1$ is negatively charge but it is also not possible because ball $1$ and $4$ also show attraction and in the end we know that ball $1$ is nor be positively or neither be negatively charge. It means be ball $1$ have no charge so it must be neutral.