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- Dictionaryspace/speɪs/
noun
- 1. a continuous area or expanse which is free, available, or unoccupied: "a table took up much of the space" Similar
- 2. the dimensions of height, depth, and width within which all things exist and move: "the work gives the sense of a journey in space and time"
verb
- 1. position (two or more items) at a distance from one another: "the poles are spaced 3m apart"
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Free space is the default environment assumed in the study of plane electromagnetic waves, as it allows for the simplest mathematical analysis and modeling of wave behavior. In free space, electromagnetic waves travel at the speed of light, which is approximately $3 \times 10^8$ m/s, and this speed is independent of the frequency or wavelength of the wave.
Vacuum permittivity, commonly denoted ε0 (pronounced "epsilon nought" or "epsilon zero"), is the value of the absolute dielectric permittivity of classical vacuum. It may also be referred to as the permittivity of free space, the electric constant, or the distributed capacitance of the vacuum. It is an ideal (baseline) physical constant.
The impedance of free space (that is, the wave impedance of a plane wave in free space) is equal to the product of the vacuum permeability μ 0 and the speed of light in vacuum c 0. Before 2019, the values of both these constants were taken to be exact (they were given in the definitions of the ampere and the metre respectively), and the value of the impedance of free space was therefore ...
- Units
- Explanation
- Vacuum Permittivity
- Relative Permittivity
- Practical Applications
- Dispersion and Causality
- Measurement
- Further Reading
- External Links
The SI unit of permittivity is farad per meter (F/m or F·m−1). 1. F m = C V ⋅ m = C 2 N ⋅ m 2 = C 2 ⋅ s 2 kg ⋅ m 3 = A 2 ⋅ s 4 kg ⋅ m 3 {\displaystyle {\frac {\text{F}}{\text{m}}}={\frac {\text{C}}{{\text{V}}{\cdot }{\text{m}}}}={\frac {{\text{C}}^{2}}{{\text{N}}{\cdot }{\text{m}}^{2}}}={\frac {{\text{C}}^{2}{\cdot }{\text{s}}^{2}}{{\text{kg}}{\cdo...
In electromagnetism, the electric displacement field D represents the distribution of electric charges in a given medium resulting from the presence of an electric field E. This distribution includes charge migration and electric dipole reorientation. Its relation to permittivity in the very simple case of linear, homogeneous, isotropic materials w...
The vacuum permittivity εo (also called permittivity of free space or the electric constant) is the ratio D/E in free space. It also appears in the Coulomb force constant, 1. k e = 1 4 π ε 0 {\displaystyle k_{\text{e}}={\frac {1}{\ 4\pi \varepsilon _{0}\ }}} Its value is 1. ε 0 = d e f 1 c 2 μ 0 ≈ 8.854 187 8128 ( 13 ) × 10 − 12 F/m {\displaystyle ...
The linear permittivity of a homogeneous material is usually given relative to that of free space, as a relative permittivity εr (also called dielectric constant, although this term is deprecated and sometimes only refers to the static, zero-frequency relative permittivity). In an anisotropic material, the relative permittivity may be a tensor, cau...
Determining capacitance
The capacitance of a capacitor is based on its design and architecture, meaning it will not change with charging and discharging. The formula for capacitance in a parallel plate capacitoris written as 1. C = ε A d {\displaystyle C=\varepsilon \ {\frac {A}{d}}} where A {\displaystyle A} is the area of one plate, d {\displaystyle d} is the distance between the plates, and ε {\displaystyle \varepsilon } is the permittivity of the medium between the two plates. For a capacitor with relative permi...
Gauss's law
Permittivity is connected to electric flux (and by extension electric field) through Gauss's law. Gauss's law states that for a closed Gaussian surface, S, 1. Φ E = Q enc ε 0 = ∮ S E ⋅ d A , {\displaystyle \Phi _{E}={\frac {Q_{\text{enc}}}{\varepsilon _{0}}}=\oint _{S}\mathbf {E} \cdot \mathrm {d} \mathbf {A} \ ,} where Φ E {\displaystyle \Phi _{E}} is the net electric flux passing through the surface, Q enc {\displaystyle Q_{\text{enc}}} is the charge enclosed in the Gaussian surface, E {\di...
In general, a material cannot polarize instantaneously in response to an applied field, and so the more general formulation as a function of time is 1. P ( t ) = ε 0 ∫ − ∞ t χ ( t − t ′ ) E ( t ′ ) d t ′ . {\displaystyle \mathbf {P} (t)=\varepsilon _{0}\int _{-\infty }^{t}\chi \left(t-t'\right)\mathbf {E} \left(t'\right)\,\operatorname {d} t'~.} ...
The relative permittivity of a material can be found by a variety of static electrical measurements. The complex permittivity is evaluated over a wide range of frequencies by using different variants of dielectric spectroscopy, covering nearly 21 orders of magnitude from 10−6 to 1015 hertz. Also, by using cryostatsand ovens, the dielectric properti...
Bottcher, C.J.F.; von Belle, O.C.; Bordewijk, Paul (1973). Theory of Electric Polarization. Vol. 1: Dielectric Polarization. Elsevier. ISBN 0-444-41579-3.(volume 2 publ. 1978)von Hippel, Arthur (1954). Dielectrics and Waves. ISBN 0-89006-803-8.von Hippel, Arthur, ed. (1966). Dielectric Materials and Applications: Papers by 22 contributors. ISBN 0-89006-805-4."Chapter 11". lightandmatter.com. Electromagnetism. Archived from the original on 2011-06-03.— a chapter from an online textbook
Therefore it follows from our definition of the amp that the permeability of free space, by definition, has a value of exactly. μ0 = 4π ×10−7 T m A−1, (7.3.1) (7.3.1) μ 0 = 4 π × 10 − 7 T m A − 1, or, as we shall learn to express it in a later chapter, 4π ×10−7 4 π × 10 − 7 henrys per metre, H m−1 H m − 1. It was ...
The vacuum characterises the least possible value of Permittivity. This is commonly referred to as the Permittivity of Free Space or electric constant, which is denoted by ϵ 0 and has the value 8.85 10-12 Farad/metre. The opposition against the formation of electric field lines is evident in dielectrics too. The permittivity of a dielectric is ...
Sep 30, 2023 · The magnetic permeability of free space (μ₀) is a fundamental constant that determines how magnetic fields are formed in a vacuum. It is also known as the vacuum permeability constant. The value of μ₀ is approximately 4π × 10 -7 N/A 2. This constant plays a crucial role in electromagnetic theory and has various applications.
