Electrostatic

Electrostatics is the branch of Physics that deals with the Force s exerted by a Static (i.e. Unchanging ) Electric Field upon Charged Object s.

OVERVIEW

In electrostatics, charge need not be 'static' in the sense of unchanging. Instead 'static' implies that the dynamic coupling between electric and magnetic fields can be ignored. In electrostatics we study e-fields, voltage, and charge, but ignore any magnetic fields generated by the motion of these charges or that may be present for other reasons. Because of the electric field's relationship to and interaction with Magnetism , electrostatics is a subfield of Electromagnetism .

The electrostatic approximation

The validity of the electrostatic approximation rests on the assumption that the electric field is Irrotational :

:

abla 	imes \mathbf{E} = 0

From Faraday's Law , this assumption implies the absence or near-absence of time-varying magnetic fields:

:

{ \partial \mathbf{B} \over \partial t} = 0

In other words, electrostatics does not require the absence of magnetic fields or electric currents. Rather, if magnetic fields or electric currents ''do'' exist, they must not change with time, or in the worst-case, they must change with time only very ''slowly''.

In some problems, both electrostatics and Magnetostatics may be required for accuratete predictions, but the coupling between the two can still be ignored.

Electrostatic potential

Because the electric field is irrotational,is possible to express the electric field as the Gradient of a scalar function, called the
Electrostatic Potential (also known as the Voltage ). Thus, the electrostatic potential Φ is related to the electric field E by the equation:

:

\mathbf{E} = - 
abla \Phi

FUNDAMENTAL CONCEPTS

Coulomb's law

The fundamental Equation of electrostatics is Coulomb's Law , which describes the force between two Point Charge s:

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Electrostatic