Every object in the universe is made up of tiny particles called atoms. Atoms contain even smaller particles called protons, neutrons and electrons. Protons carry a positive charge, neutrons carry no charge, and electrons carry a negative charge. We know that particles with like charges repel each other and particles with opposites charges attract. Likewise, we know that protons repel other protons but attract electrons, and that electrons repel other electrons but attract protons.
Most objects contain the same number of protons and elec-trons and, therefore, carry no charge.
For example, neither a plastic comb nor your hair carry a charge under normal circumstances. But when you comb your hair and then move your comb away from your hair, sometimes the hair is attracted to the comb. During combing, some of the electrons in the atoms of your hair are transferred to the comb. Since your hair loses electrons, or negative charges, it is left with a positive charge after combing. Since the comb gained electrons, it is left with a negative charge.