Question

To get to our goal of determining why we keep the container on the ground and the nozzle in contact with it while fueling, we explore a number of electrostatic phenomena from our everyday experiences.

Initially a boy's hair lies flat, and a plastic comb is unable to attract bits of paper. Then the comb is run through the boy's hair as shown in the figure. Afterward his hair stands upward.

The photograph shows a person running a plastic comb through the hair on top of a boy's head such that his hair is pulled up away from his head. Some additional flyaway hairs are seen rising toward the comb.

Why does his hair stand upward afterward? Consider the statements below and use one or more of them to give a correct explanation. Check all that you will use in your explanation.

The plastic comb is a good conductor. Rubbing the comb through the hair transfers charged particles from the comb to the hair or perhaps from the hair to the comb. Initially the hair is neutral. The Earth acts as a reservoir or ground, transferring charged particles to or from the hair as required. Initially the comb is neutral. On the microscopic level the molecules in the hair and the comb can be modeled as small hooks that attach to one another.

Answer 1

Rubbing the comb through the hair transfers charged particles (electrons) from the hair to the comb. So, the comb becomes negtively charged and hair becomes positively charged. Hence, both attract each other. Comb can also attract pieces of paper.

Therefore, the following options are correct,

(i) Rubbing the comb through the hair transfers charged particles from the comb to the hair or perhaps from the hair to the comb.

(ii) Initially the hair is neutral.

(iii) Initially the comb is neutral.