There are only two kinds of electrical charge: negative (-) and positive (+). Opposite charges attract one another, and like charges repel. In addition, the closer the charges are together, the greater the force of attraction or repulsion. If the distance between a + and - charge is cut in half, the force of attraction increases four-fold. If the distance between the charges doubles, the force of attraction is then only one-fourth of what it was. This is referred to as inverse-square behavior. If the separation of a + and a - charge increases three-fold, the force changes to (1/3)2, or 1/9 of what it was.