The next long-range force we'll look at is one that exists between electrically charged particles. This is called an electric or electrostatic force. But before we get to the force law, we need to explain a few facts about electric charges.
Electric charge is a physical property of particles just like mass is. Elementary particles, the fundamental building blocks of matter, are frequently charged. For example, electrons are particles that orbit the nuclei of atoms, and they have negative charge. The nuclei of atoms include protons, which have positive charge, and neutrons, which have zero charge. What we call an electric current is actually a flow of free electrons in a metal—moving charges (whether electrons ...