Electric Charge and Static Electricity

1. A plastic rod is rubbed with a piece of wool. If the plastic rod becomes negatively charged, what charge does the wool acquire, and why?

2. Two balloons are rubbed against a student's hair, giving them both a negative charge. If the balloons are then hung from strings close to each other, will they attract, repel, or remain stationary? Explain your answer.

3. A neutral metal sphere is touched by a positively charged rod. What will be the charge of the metal sphere after the rod is removed? Explain the process that leads to this charge.