Question

Wrap up question 1: You hold a “Top” piece of charged tape near an uncharged soda can. Describe the behavior of the tape. Would the behavior be different if you used a “Bottom” piece of tape instead? Explain.

Wrap up question 2: Suppose there exists a third type of charge in addition to the two types we associate with glass and plastic. Call this third type X charge. What experiment(s) could you use to test whether an object has X charge? State clearly how the outcome(s) of the experiment(s) would be interpreted.

Wrap up question 3: A positively charged electroscope has separated leaves. Describe what will happen if you bring a negatively charged rod near, but not touching, the top of the electroscope.

Answer 1

1] A charged surface (tape) holds only one charge throughout its surface which induces a charge of the opposite kind in the previously uncharged soda can.

If the top side is replaced by the bottom side, the same charge on the tape will induce a charge in the uncharged soda. This situation is the same as before.

2] If there exists a charge of the 3rd kind (but not a 4th charge), it must get attracted to both positive and negative charges. To test this, suspend this material with the charge of this kind by a thread and introduce either of the positive or negative charges. If the material shows attraction for both cases, it is proven that the charge is of the 3rd kind.

3] If you bring a negatively charged rod near the positively charged electroscope, the top part of the electroscope (closer to the rod) will become partially negative which implies that negatively charged leaves now have smaller amount of charge on them and so their repulsion will decrease. Therefore, the leaves will come close to each other.