Recall that electrons are negatively charged particles while protons are positively charged particles. An electrical charge is created when an object has either an excess (negative charge) or a deficiency (positive charge) of electrons. You may recall an important and fundamental electrical law from your physics studies that:
Like charges repel each other.
Unlike charges attract each other.
Remember charging a balloon by rubbing it on your hair? The balloon becomes negatively charged, while the hair is positively charged. Holding the balloon near a neutral object will make the charges in that object move. As you rub the balloon on your hair, the balloon acquires a negative charge because some electrons (negatively-charged) in your hair are transferred to the balloon. Your hair would have insufficient number of electrons, thereby not maintaining its electrical neutrality. You can think of removing electrons from your hair as removing negative charges that, in turn, results to a net positive charge in your hair. The fundamental unit of charge, which is the coulomb, is named after the French scientist Charles Coulomb. It is an International System of Units (SI) basic unit used in measuring charge.
