Chapter 16, Problem 4Q

Why does a plastic ruler that has been rubbed with a cloth have the ability to pick up small pieces of paper? Why is this difficult to do on a humid day?

To determine

Why does a plastic ruler that has been rubbed with a cloth have the ability to pick up small pieces of paper? Why is this difficult to do on a humid day?

Answer to Problem 4Q

Solution:

Due to charges attached with that when rubbed with hair and negative positive charges attract each other at humid our hairs are clean from charges.

Explanation of Solution

A plastic ruler is rubbed, free electrons travel from cloth to the ruler. The cloth loses electrons becomes positive, ruler gains electrons becomes negative. The ruler's negative charge polarizes the charge on the paper, so basically it attracts the positive charges and repels the electrons. Enough electric force is created and lifts the paper. On a humid day there are more water molecules in the air. Water molecules are polar where there is an uneven distribution of charge. The oxygen is more negative and the hydrogen's are more positive. The free charges on the ruler are attracted to the water molecules and the ruler has a smaller charge. Thus, the paper will be less polarized and the electric force created will not be sufficient. Due to charges attached with that when rubbed with hair and negative positive charges attract each other at humid our hairs are clean from charges.