An Etymological Dictionary of Astronomy and Astrophysics
English-French-Persian

A substance in which an electric field gives rise to no net flow of electric charge but to a displacement of charge in opposite directions. The displacement is usually small compared to atomic dimensions. Dielectrics differ from conductors in that they have no free electrons to move through the material under the influence of an electric field. Most insulating materials, e.g. air, porcelain, mica, glass, are dielectrics. A perfect vacuum would constitute a perfect dielectric. → diamagnetic.

Dielectric, from Gk. dia- a prefix used with several meanings "passing through; thoroughly; completely; going apart," and in the present case "not, opposed;" → electric.

Nâbarg, from nâ- "not," → un-, + barq→ electricity.

Pertaining to, derived from, produced by, or associated with electricity.

Term coined in by the English physicist William Gilbert (1540-1603) in treatise De Magnete (1600), from L. electrum "amber," from Gk. elektron "amber."

Barqi, adj. of barq, → electricity.

A luminous and extremely hot electrical → discharge between two → electrodes when an ionized → plasma is created in the air or gas across the electrodes.

→ electric; → arc.

The intrinsic property of matter responsible for all electric phenomena, occurring in two forms arbitrarily designated → negative and → positive.

→ electric; → charge.

Physics: A closed path followed by an → electric current; a number of → conductors interconnected for the purpose of carrying an electric current.

→ electric; → circuit.

The → rate at which → electric charge → flows past a given point through a → conductor, measured in → amperes.

→ electric; → current.

1) A type of → charge distribution consisting of two charges, a positive and a negative charge of the same magnitude separated by a distance s, which is small compared to the distance r to the point P at which the → electric potential is V and the → electric field intensity is E.The potential falls as the square of the distance (1/r²) and the electric field intensity decreases as the cube of the distance (1/r³).
2) A simple → antenna consisting of a pair of oppositely charged → conductors capable of radiating an → electromagnetic wave in response to the movement of an electric charge from one conductor to the other.

→ electric; → dipole.

The flow of electricity through a gas, resulting in the emission of radiation that is characteristic of the gas and of the intensity of the current.

→ electric; → discharge.

The effect produced by the existence of an → electric charge in the volume of space that surrounds it. The direction of the field is taken to be the direction of the force it would exert on a positive test charge. The electric field is radially outward from a positive charge and radially in toward a negative point charge.

→ electric; → field.

The strength of an electric field at any point as measured by the force exerted upon a unit positive charge placed at that point.

→ electric; → intensity.

An electric → charge distribution consisting of more than four → positive and → negative → electric charges located at a small distance from each other. The multipole concept is an extension of the → electric quadrupole. For the generalized multipole characterized by the letter l, the potential at a distance r varies as 1/r^{l + 1} and the field intensity as 1/r^{l + 2}.

→ electric; → multipole.

The amount of → work required to move a unit → electric charge from → infinity to a specific point against an → electric field. The → SI unit of electric potential is → joules per → coulomb, otherwise known as → volt.

→ electric; → potential.

A potential φ defined so that the → electric field  E is expressed by a combination of its → gradient and the variation of the → magnetic vector potential over time: E = -∇φ -∂A/∂t.

→ electric; → scalar; → potential.

Of, relating to, or concerned with electricity; electric.

→ electric + → -al.

A measure of a material's ability to conduct an electrical current. It is the reciprocal of the → resistivity. Conductivity is expressed by σ = ne²l/(2mv), where n is the number of electrons per cm³ volume of the → conductor, e is the → electron charge, l is the → mean free path, m is the → electron mass, and v is the arithmetic mean velocity of thermal motion of electrons at a given temperature.

→ electrical; → conductivity.

An arrangement of the various electrical energy sources with interconnected electrical devices.

→ electric; → network.

1) The physical phenomena arising from the behavior of → electrons and → protons that is caused by the → attraction of particles with opposite → charges and the → repulsion of particles with the same charge.
2) The → science of electric charges and → currents.
3) A → flow of electrons that is used to generate → light and → power electric devices.

From L. electrum "amber," from Gk. elektron "amber" + -ity a suffix used to form abstract nouns expressing state or condition.

Barq, Pers. term, used also in Ar. and Hebrew (barak "lightening"); variants in Pers.: varq, barx, balk, belak, bala; Lârestâni belak; Tabari, Lahijâni, Semnâni, Sorxeyi, Sangesari belk; Gilaki val; Lori beleyz; Kurd. bilese; Tokharian AB pâlk; Mid/Mod.Pers. bir "lightening," Mid.Pers. brâh "brilliance, splendour," br'z- "to shine, beam," Mod.Pers. barâz "beauty, grace, elegance;" Av. brāz- "to shine, beam; splendour," brazāiti "shines;" cf. Skt. bhrāj- "to shine, beam, sparkle," bhrajate "shines;" Gk. phlegein "to burn;" L. fulgere "to shine," fulmen "lightning," flagrare "to blaze, burn;" O.H.G. beraht "bright;" O.E. beorht "bright;" E. → bright; PIE base *bherəg-; *bhrēg- "to shine; white."

The → photoelectric effect in solids where free electrons are emitted from the surface of a substance (e.g., → semiconductor) when radiation of appropriate frequency falls on it. Also called → photoemissive effect.

→ external; → photoelectric; → effect.

Characterized by the presence of a spontaneous → electric dipole while not exposed to an external electric field. → ferroelectricity.

→ ferro-; → electric.

A property observed in certain materials characterized by the presence of a spontaneous electric polarization even in the absence of an external electric field. In the ferroelectric state the center of positive charge of the material does not coincide with the center of negative charge. This phenomenon is explained by spontaneous alignment of these permanent moments along the same direction. The term comes from the similarity with → ferromagnetism, but iron is not a ferroelectric. Ferroelectricity disappears above a critical temperature. Ferroelectric materials have been a fertile field for the study of → phase transitions.

→ ferro-; → electricity.