Suppose that you have a rod that is positively charged, a rod that is negatively charged and a stand that allows rotation. If you are handed a polystyrene rod of unknown charge-state, how could you determine if it has a positive charge, a negative charge or if it is uncharged? Explain what happens to the unknown rod if it has a positive charge, a negative charge or if it is uncharged.

Explanation:

A charge is produced when an atom losses or gains an electron. The law of static electricity states that like charges repels, while unlike charges attracts.

1. To determine the charge on the polystyrene rod.

Place the polystyrene rod on the non-conducting rotating stand, and bring the positively charged rod close to it. If attraction occurs, it shows that it is oppositely charged. If repulsion occurs, it shows that it is positively charged.

Bringing a negatively charged rod close to the rotating polystyrene rod would attract it if the charge is opposite. But if the charge on the two rods are the same, repulsion occurs.

2a. When the polystyrene rod is positively charged, it would attract the negatively charged rod but repel the positively charged rod.

b. When the polystyrene rod is negatively charged, it would repel the negatively charged rod but attract the positively charged rod.

c. When the polystyrene rod is uncharged, no reaction would be observed when either the positively charged or negatively charged rod is brought close to it.