| 单词 |
permittivity |
| 释义 |
permittivity Physics.|pɜːmɪˈtɪvɪtɪ|
[f. permit v. + -ivity.]
One of the physical parameters of a medium, equal to the ratio of the electric displacement D to the electric field strength E at any point in it; also (more fully relative permittivity), the ratio of the permittivity of a medium to the permittivity of free space: = dielectric constant; permittivity of free space, a constant ε0 which in the C.G.S. electrostatic system of units is unity and in the International System of Units is 1/µ0c2 (= 8·854 × 10-12) farad per metre, where µ0 is the permeability of free space and c is the speed of light.
1887O. Heaviside in Electrician 17 June 124/1 Nomenclature Scheme... Permittance. Permittivity. 1890[see elastance]. 1938G. P. Harnwell Princ. Electr. & Electromagn. i. 12 If the charges are measured in coulombs and if r is in meters and F in newtons, the constant κ0 has the value κ0 = ..8·85 × 10-12 farads/meter... This constant..is known as the permittivity of free space. 1944Phil. Mag. XXXV. 83 Guggenheim has suggested the term permittivity for the fundamental quantity and specific inductive capacity or dielectric constant for the derived quantity. In conformity with the other suggestions in this paper it would be more uniform to adopt permittivity and relative permittivity... Similarly in the magnetic case we have permeability and relative permeability. 1946Nature 6 July 33/2 The paper contains a description of apparatus used for measurements at frequencies of about 3,000 Mc./s{ddd}and a statement of typical experimental results obtained with a specimen of polythene, which at the above frequency had a permittivity of 2·27. 1962Corson & Lorrain Introd. Electromagn. Fields ix. 317 The permittivity of free space ε0 can..be determined directly from measurements involving electrostatic phenomena. 1971Engineering Apr. 44/1 The capacitance C (microfarads) of a parallel plate capacitor..is..proportional to the relative permittivity εr of the dielectric medium. 1974Harvey & Bohlman Stereo F.M. Radio Handbk. vii. 148 Because of the presence of water vapour in particular, the permittivity of the air in the troposphere is greater than unity. |
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