A person has long hair hanging straight down from their head. A second person rubs a balloon with felt so that the balloon is ne
gatively charged, then brings it near the first person's hair without allowing the balloon to touch the hair. They notice that strands of the first person's hair are attracted to the balloon. The second person then rubs another balloon with plastic wrap so that it is positively charged, and again they notice that the balloon attracts strands of the first person's hair. Which is the best explanation for the attraction of the hair to the balloon
<em>The best explanation is that the first person is grounded to the earth, and his/her body either draws up negative charges from the earth, or tend to conducts negative charges to the earth, depending on the charge on the balloon.</em>
Explanation:
The earth is an infinite store for charges. In the first case where the second person brings a negatively charged balloon towards the first person, the negative charges on the balloon induces the first person's body to tend to attract the negative charges on the balloon through the first person's body to the positive charges within the earth. In the second case when again a positively charged balloon is brought near the first person's hair, the positive charges on the balloon induce the first person's body into drawing up negative charges from within the earth. This charges, and their opposite induced charges, create an attractive force between the hair strands and the balloons.
Electrostatic repulsion is the force between two charges having the same sign, that tends to separate them further. The force is proportional to the product of the charges, and inversely proportional to the square of the distance between them.
