# Electrostatic Field

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## electrostatic field

[i‚lek·trə′stad·ik ′fēld]## Electrostatic Field

an electric field that consists of stationary electric charges interacting with each other. Like a variable electric field, an electrostatic field may be characterized by electric field strength E, which is the ratio of the force acting on a charge to the magnitude of the charge. The lines of force, which determine the field strength, are not closed: they extend from positive charges to negative charges. In dielectrics, the electrostatic field is characterized by the vector D, known as electric flux density (*see*INDUCTION, ELECTRICAL AND MAGNETIC), which satisfies Gauss’ theorem.

An electrostatic field is a potential field; that is, the work of the field in moving an electric charge between two points does not depend on the shape of the trajectory. Over a closed path, the work is equal to zero. Owing to its potential character, an electrostatic field can be represented by a single scalar function—the electrostatic potential φ, which is related to the vector **E** by the equation **E** = – grad φ. The potential φ satisfies Poisson’s equation.

In a homogeneous dielectric, the electrostatic field is decreased by a factor oft, where e is the permittivity. The electrostatic field inside a conductor is equal to zero, whereas all points on the conductor’s surface have the same potential φ. If there is a cavity in the conductor, the electrostatic field in the cavity is also equal to zero. Electrostatic shielding is based on the latter phenomenon.