dielectric, n. and a.
(daɪɪˈlɛktrɪk)
[f. di- prefix3 = Gr. δι-, δια- through + electric.]
A. n. A substance or medium through or across which electric force acts without conduction; a non-conductor; an insulating medium.
| 1837 Faraday in Phil. Trans. (1838) I. 25 The particular action described occurs in the shell-lac..as well as in the dielectric used within the apparatus. 1838 ― Exp. Res. (1839) 364 My view that electric induction is an action of the contiguous particles of the insulating medium or dielectric. Note. I use the word dielectric to express that substance through or across which the electric forces are acting. (Dec. 1838.) 1881 Maxwell Electr. & Magn. I. 462 The resistance of the greater number of dielectrics diminishes as the temperature rises. 1885 Watson & Burbury Math. Th. Electr. & Magn. I. 184 The dielectric, in Faraday's language, has inductive capacity. It is less for air and the permanent gases than for any solid dielectrics, and rather less for vacuum than for air. |
B. adj.
1. Having the property of transmitting electric effects without conduction; non-conducting.
| 1871 Athenæum 10 June 723 He supposes..that the sheaths of the muscular fibres are dielectric. 1885 Watson & Burbury Math. Th. Electr. & Magn. I. 77 Such a medium, considered as transmitting these electrical effects without conduction, is called a Dielectric medium, and the action which takes place through it is called..Induction. |
2. a. Relating to a dielectric medium, or to the transmission of electricity without conduction.
| 1863 Atkinson tr. Ganot's Physics (1886) 685 The action is..analogous to that of the pole of a magnet on a piece of soft iron; and Faraday called it dielectric polarisation. 1881 Macfarlane in Nature No. 620. 465 By the dielectric strength of a substance I mean the ratio of the difference of potential required to pass a spark through air under the same conditions. 1881 Athenæum 5 Feb. 203/2 [A paper on] ‘Dielectric Capacity of Liquids’, by Dr. Hopkinson. |
b. dielectric constant: one of the physical parameters of a non-conducting medium, equal to the ratio of the electric displacement at any point in the medium to the displacement an identical charge distribution would produce in a vacuum, measured at the same point; the relative permittivity. (Some writers call this the relative dielectric constant, using dielectric constant for the ratio of electric displacement to electric field strength: cf. permittivity.)
| 1875 Jrnl. Chem. Soc. XXVIII. 38 (heading) Experimental determination of the dielectric constants of insulators. 1893 E. Atkinson tr. Ganot's Elem. Treat. Physics (ed. 14) ix. iii. 734 In crystallised bodies the dielectric constant varies with the direction of the axes. 1936 Hausmann & Slack Physics xxiii. 445 The dielectric constant..is very nearly unity (1·000586) for air at normal temperature and pressure. 1943 Electronic Engin. XVI. 206 The physical constant associated with a dielectric is called the dielectric constant. This is generally defined as the ratio of the capacitance of a condenser with the dielectric material between the electrodes to the capacitance of the electrodes alone when placed in vacuo. 1955 C. P. Smyth Dielectric Behavior & Struct. i. 1 In the m.k.s. system the dielectric constant of free space is 8·854 × 10-12 farad per m. 1959 B. I. & B. Bleaney Electr. & Magn. xvi. 454 The dielectric constant of a substance affords some valuable information as to the structure of its constituent molecules. 1967 M. Nelkon Fund. Physics xxxvi. 673 Mica has a higher dielectric constant of 7. |
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▸ dielectric heating n. heating produced by subjecting an electrically insulating material to high-frequency electromagnetic radiation; also called electronic heating.
| 1940 Proc. Physical Soc. 52 485 The author suspects that most of this rise in temperature is due to ‘dielectric heating’ and not much to viscous absorption of the supersonics. 1947W. J. Brierley in P. I. Smith Pract. Plastics xxii. 295/1 By the use of radio-frequency heating, sometimes termed dielectric heating or diathermy, the heat is generated internally in the pack and the glue line becomes five to fifteen degrees hotter than the wood veneer. 2008 Internat. Jrnl. Fatigue 30 306/1 For tests of parts made of ceramic materials, it is recommended in a number of papers to use dielectric heating. |