electric field
(noun)Definition of electric field
A region of space around a charged particle, or between two voltages; it exerts a force on charged objects in its vicinity.
Source: Wiktionary  CC BYSA 3.0
Examples of electric field in the following topics:

Electric Flux
 Electric flux is the rate of flow of the electric field through a given area (see ).
 Electric flux is proportional to the number of electric field lines going through a virtual surface.
 If the electric field is uniform, the electric flux passing through a surface of vector area S is $\Phi_E = \mathbf{E} \cdot \mathbf{S} = ES \cos \theta$ where E is the magnitude of the electric field (having units of V/m), S is the area of the surface, and θ is the angle between the electric field lines and the normal (perpendicular) to S.
 For a nonuniform electric field, the electric flux dΦE through a small surface area dS is given by $d\Phi_E = \mathbf{E} \cdot d\mathbf{S}$ (the electric field, E, multiplied by the component of area perpendicular to the field).
 While Gauss' Law holds for all situations, it is only useful for "by hand" calculations when high degrees of symmetry exist in the electric field.
 Electric flux is the rate of flow of the electric field through a given area.

Uniform Electric Field
 A uniform field is that in which the electric field is constant throughout.
 Equations involving nonuniform electric fields require use of differential calculus.
 Uniformity in an electric field can be approximated by placing two conducting plates parallel to one another and creating a potential difference between them.
 The equation for magnitude of a uniform electric field is: $E=\frac {\Delta \phi}{d}$ where E is the field, Δ is the potential difference between the plates, and d is the distance between the plates.
 Uniformity of an electric field allows for simple calculation of work performed when a test charge is moved across it.
 An electric field that is uniform is one that reaches the unattainable consistency of being constant throughout.

Electric Field from a Point Charge
 The electric field of a point charge is, like any electric field, a vector field that represents the effect that the point charge has on other charges around it.
 Given a point charge, or a particle of infinitesimal size that contains a certain charge, electric field lines emanate radially in all directions.
 The reason for these directions can be seen in the derivation of the electric field of a point charge.
 The constant k is a result of simply combining the constants together, and q is the charge of the particle creating the electric field.
 The above mathematical description of the electric field of a point charge is known as Coulomb's law.
 A point charge creates an electric field that can be calculated using Coulomb's law.

Stress and Strain
 The electric field of a point charge is, like any electric field, a vector field that represents the effect that the point charge has on other charges around it.
 Given a point charge, or a particle of infinitesimal size that contains a certain charge, electric field lines emanate radially in all directions.
 The reason for these directions can be seen in the derivation of the electric field of a point charge.
 Let's first take a look at the definition of electric field of a point particle, $\vec{E} = \frac{1}{4\pi\epsilon_o}\frac{q}{r^2}\hat{r} = k\frac{q}{r^2}\hat{r}$.
 The above mathematical description of the electric field of a point charge is known as Coulomb's Law.
 A point charge creates an electric field that can be calculated using Coulomb's Law.

Gauss's Law
 Gauss's law, also known as Gauss's flux theorem, is a law relating the distribution of electric charge to the resulting electric field.
 In words, Gauss's law states that: The net outward normal electric flux through any closed surface is proportional to the total electric charge enclosed within that closed surface.
 Each of these forms in turn can also be expressed two ways: In terms of a relation between the electric field E and the total electric charge, or in terms of the electric displacement field D and the free electric charge.
 Gauss's law is a law relating the distribution of electric charge to the resulting electric field.

A Microscopic View: Drift Speed
 To be precise, this rapidly moving signal or shock wave is a rapidly propagating change in the electric field .
 However, there is an electric field in the conductor that causes the electrons to drift in the direction shown (opposite to the field, since they are negative).
 The drift velocity vdis the average velocity of the free charges after applying the field.
 Current density is the electric current per unit area of crosssection.
 The drift velocity is the average velocity that a particle achieves due to an electric field.

Conductors and Fields in Static Equilibrium
 If conductors are exposed to charge or an electric field, their internal charges will rearrange rapidly.
 Similarly, if a conductor is placed in an electric field, the charges within the conductor will move until the field is perpendicular to the surface of the conductor.
 Negative charges in the conductor will align themselves towards the positive end of the electric field, leaving positive charges at the negative end of the field.
 The conductor thus becomes polarized, with the electric field becoming stronger near the conductor but disintegrating inside it.
 This occurrence is similar to that observed in a Faraday cage, which is an enclosure made of a conducting material that shields the inside from an external electric charge or field or shields the outside from an internal electric charge or field.
 In the presence of charge or an electric field, the charges in a conductor will redistribute until they reach static equilibrium.

Electric Field and Changing Electric Potential
 Any charge will create a vector field around itself (known as an electric field).
 Electric field is the gradient of potential, which depends inversely upon distance of a given point of interest from a charge.
 As the test charge moves, the potential between it and another charge changes, as does the electric field.
 The relationship between potential and field (E) is a differential: electric field is the gradient of potential (V) in the x direction.
 Thus, as the test charge is moved in the x direction, the rate of the its change in potential is the value of the electric field.
 Electric field is the gradient of potential, which depends inversely upon distance of a given point of interest from a charge.

Energy Conservation
 Energy is conserved in the movement of a charged particle through an electric field, as it is in every other physical situation.
 This phenomenon can be expressed as the equality of summed kinetic (Ekin) and electric potential (Eel) energies: $(E_{kin}+E_{el})_{initial}=(E_{kin}+E_{el})_{final}$ Given a stationary test charge in a certain location, an applied electric field will cause the charge to move to one end or the other, depending on the charge (positive test charges will move in the direction of the field; negative charges will move in the opposite direction).
 At the instant at which the field is applied, the motionless test charge has 0 kinetic energy, and its electric potential energy is at a maximum.
 Another way to express the previous equation is: $(\frac {1}{2}mv^2+U)_{initial}=(\frac {1}{2}mv^2+U)_{final}$ where m and v are the mass and velocity of the electron, respectively, and U is the electric potential energy.
 Energy is conserved in the movement of a charged particle through an electric field, as it is in every other physical situation.

Electrostatic Shielding
 Electrostatic shielding is the phenomenon that is observed when a Faraday cage operates to block the effects of an electric field.
 Such a cage can block the effects of an external field on its internal contents, or the effects of an internal field on the outside environment.
 This type of cage was first invented by Michael Faraday in 1836, and can block external static and nonstatic electric fields.
 When an external electric field operates on a Faraday cage, the charges within the cage (which are mobile, as the cage is a conductor) rearrange themselves to directly counteract the field and thus "shield" the interior of the cage from the external field The action of a Faraday cage may depend on whether or not it is grounded.
 Electrostatic shielding is the phenomenon that occurs when a Faraday cage blocks the effects of an electric field.