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Electrostatics.................

Electrostatics

The fundamental equations of electrostatics are linear equations,

(SI units),

(Gaussian units).

The principle of superposition holds.

The electrostatic force on a particle with charge q at position r is F=qE(r).

.

f is the electrostatic potential.

Important formulas:

The field at r due to a point charge at r?:

(Omit the factor

to obtain the corresponding expressions in Gaussian units.)

The field of a charge distribution:

(We consider volume, surface, and line charge distributions and point charges.)

The potential at r due to a point charge at r?:

The potential of a charge distribution:

Gauss? law:

(SI units),

(Gaussian units).

In situations with enough symmetry, Gauss? law alone can be used to find E.

The electrostatic energy of a charge distribution:

or, for a continuous charge distribution,

(SI units),

(Gaussian units).

Dipoles

The field of a dipole at the origin:

The potential of a dipole at the origin:

The force on a dipole:

The torque on a dipole:

The energy of a dipole in an external field:

Properties of conductors in electrostatics

	E=0 inside.
	r =0 inside.
	Any excess charge resides on the surface.
	E on the surface is perpendicular to the surface.
	(SI units), (Gaussian units), just outside the surface.

Dielectrics

The polarization

is defined as the dipole moment per unit volume.

The total charge density is due to free and to bound (polarization) charges.

.

(SI units),

(Gaussian units).

For linear, isotropic, homogeneous (lih) dielectrics we have

,

.

Boundary conditions in electrostatics

(SI units),

,

f is continuous across the boundary.

(Gaussian units),

,

f is continuous across the boundary.

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Community Contributions - Articles by goIITians

Important formulas:

Dipoles

Properties of conductors in electrostatics

Dielectrics

Boundary conditions in electrostatics