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.
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.
Fr.: arc électrique
bâr-e barqi (#)
Fr.: charge électrique
Fr.: circuit électrique
jarayân-e barq (#)
Fr.: courant électrique
dipol-e barqi, diqotbe-ye ~
Fr.: dipôle électrique
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).
Fr.: décharge électrique
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.
meydân-e barqi (#)
Fr.: champ électrique
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.
dartanuyi-e barqi (#)
Fr.: intensité électrique
The strength of an electric field at any point as measured by the force exerted upon a unit positive charge placed at that point.
Fr.: multipôle électrique
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/rl + 1 and the field intensity as 1/rl + 2.
Fr.: potentiel électrique
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 scalar potential
tavand-e marpeli-ye barqi
Fr.: potentiel électrique scalaire
Of, relating to, or concerned with electricity; electric.
Fr.: conductivité électrique
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.
Fr.: réseau électrique
An arrangement of the various electrical energy sources with interconnected electrical devices.
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.
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."
external photoelectric effect
oskar-e šid-barqi-ye boruni
Fr.: effet photoélectrique externe
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.
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.