The plastic comb has been used to comb hair and it now picks up small plastic balls - Junior Cycle Science - Question 6 - 2011

The plastic comb picks up small plastic balls due to the phenomenon of static electricity. When the comb is used to comb hair, friction occurs between the comb and the hair, which causes electrons to be transferred from one material to the other. As a result, the comb becomes negatively charged while the hair becomes positively charged.

This charge imbalance leads to the production of static electricity. When the charged comb is brought near the small plastic balls, the negative charges on the comb induce a positive charge on the surfaces of the balls. The attraction between these opposite charges causes the comb to pick up the small plastic balls.

In summary, the combination of friction, electron transfer, and the resulting static electricity is why the plastic comb is able to attract and pick up small plastic balls.