Question

A student wins a trophy. It is a metal cup on a black plastic base. The student cleans the trophy. She holds one of the metal handles and rubs the rest of the trophy with a dry cloth. Why the plastic base does becomes negatively charged? B) The metal cup does not become charged when she rubs the trophy. Suggest why the cup does not become charged.

Answer 1

Answer:

  In this given statement , the plastic base becomes negatively charged because  plastic is an insulator . And the metal cup does not become charged because  metal is a conductor.                              

Explanation:

Reason behind , why plastic base becomes negatively charged -: When a plastic base is rubbed with a dry cloth in the metal trophy, electrons are shifted from one material to the other. Thus, the substance that gains electrons (which is the plastic base) becomes negatively charged. thus , the plastic is an insulator , which causes charge (negative ) by rubbing.

Reason behind , why the metal cup does not become charged -:  The metal cup is a conductor, and the surplus charge on the metal flows to the person who charges the cup and to the ground so that it is not charged. Thus, rubbing a metal can trigger hand\finger injury because metals generate excess heat in rubbing .