There are two kinds of charges--positive and negative. Like charges
repel one another, opposite charges attract. In materials, there are almost
exactly equal proportions of positive and negative charges, making the
materials as a whole electrically neutral. Negative charges, being associated
with electrons, are far more mobile in materials than positive charges
are. A very small excess or deficit of negative charges in a material produces
noticeable electric forces.
NSES Content Standard B
Physical Science: Motions and forces Grades 9-12, page 180 The electric force is a universal force that exists between any two charged objects. Opposite charges attract while like charges repel. The strength of the force is proportional to the charges, and, as with gravitation, inversely proportional to the square of the distance between them. |