electrostatics, study of phenomena associated with charged bodies at rest (see charge; electricity). A charged body has an excess of positive or negative charges, a condition usually brought about by the transfer of electrons to or from the body. Such bodies exert forces on each other, as described by Coulomb's law, and their behavior can be analyzed in terms of the concept of an electric field surrounding any charged body such that another charged body located at any point in the field is subject to a force proportional to the magnitude of its charge and its attraction or repulsion, depending on the polarity of the charge. The combined electric field in a given region depends on the location, magnitude, and polarity of the charges in that region. Electric fields need not be constant with time. Time-varying electric fields are used in some devices that accelerate charged atomic particles. Electrostatics has many other applications, ranging from the analysis of phenomena such as thunderstorms to the study of the behavior of electron tubes.