Electrostatics

Electrostatics is the study of electric charges at rest and the forces, fields, and potentials they produce. Charge exists in two forms, positive and negative, carried respectively by protons and electrons within atoms. Like charges repel and unlike charges attract. An object becomes charged when electrons are transferred to or from it, and this static electricity often appears when two materials are rubbed together, leaving one with a surplus and the other with a deficit of electrons.

The force between two point charges is given by Coulomb's law: the force is proportional to the product of the charges and inversely proportional to the square of the distance between them, directed along the line joining them. Charge is conserved, never created or destroyed but only moved. Materials are classed as conductors, in which charge moves freely, or insulators, in which it stays put; a nearby charge can also rearrange the charges in a conductor to give it an induced charge without direct contact.

To describe how a charge influences the space around it, physicists use the electric field, defined at each point as the force per unit charge on a small positive test charge placed there. Related to the field is the electric potential, the energy per unit charge, whose differences are measured as voltage. A powerful tool for symmetric arrangements of charge is Gauss's law, which relates the electric field passing through a closed surface to the total charge enclosed within it, often simplifying calculations that would otherwise be difficult.

Frequently asked questions

What is static electricity?

Static electricity is an imbalance of electric charge on an object's surface, often produced when materials are rubbed together and electrons are transferred from one to the other.

What does Coulomb's law describe?

It describes the force between two point charges. The force grows with the product of the charges and falls off with the square of the distance between them.

What is Gauss's law used for?

Gauss's law relates the electric field through a closed surface to the charge inside it. It greatly simplifies finding fields for symmetric charge distributions.