Point charge
A point charge is an idealized model of a particle which has an electric charge. The charge is assumed to be confined to an infinitely small region of space from which a completely uniform electric field surrounds the point.
When describing physical phenomena, such as point charges, generalized functions are especially useful. The fundamental equation of electrostatics is Coulomb's law, which describes the force between two point charges. The electric potential difference between two points is defined as the work done per unit charge (against electrical forces) in moving a positive point charge slowly between two points.
The electric field associated with a point charge is infinite at the location of the point charge. A consequence of this apparent physical paradox is that the electric field of a point-charge can only be described in a limiting sense by a carefully constructed Dirac delta function. This mathematically inelegant but physically useful concept allows for the efficient calculation of the associated physical conditions while conveniently sidestepping the philosophical issue of what actually occurs at the infinitesimally-defined point: a question that physics is as of yet unable to answer. Fortunately, a consistent theory of quantum electrodynamics developed in part by Richard Feynman removes the need for infinitesimal point charges altogether.
Earnshaw's theorem states that a collection of point charges cannot be maintained in an equilibrium configuration solely by the electrostatic interaction of the charges. In the crystal field theory, the metal ion is assumed to be free in gas form, the ligands are assumed to behave like point charges and it is assumed that the orbitals of the metal and the ligands do not interact.
See laso
External articles
- Eric W. Weisstein, "Point Charge".
- "Multiple Point Charges". HyperPhysics.
- Richard Fitzpatrick, "Electric potential energy and electric potential; [The electric potential of a point charge]". Electromagnetism and Optics, non-calculus survey course.