Search results
Results from the WOW.Com Content Network
The vacuum magnetic permeability (variously vacuum permeability, permeability of free space, permeability of vacuum, magnetic constant) is the magnetic permeability in a classical vacuum. It is a physical constant , conventionally written as μ 0 (pronounced "mu nought" or "mu zero").
A practical unit for permeability is the darcy (d), or more commonly the millidarcy (md) (1 d ≈ 10 −12 m 2). The name honors the French Engineer Henry Darcy who first described the flow of water through sand filters for potable water supply. Permeability values for most materials commonly range typically from a fraction to several thousand ...
Conductance is also a useful concept in the design and study of vacuum systems. Such systems consist of vacuum chambers and the various flow passages and pumps that connect and maintain them. These systems are common in physical science laboratories and many laboratory apparatus as well, such as mass spectrometers.
In SI units, permeability is measured in henries per meter (H/m), or equivalently in newtons per ampere squared (N/A 2). The permeability constant μ 0, also known as the magnetic constant or the permeability of free space, is the proportionality between magnetic induction and magnetizing force when forming a magnetic field in a classical vacuum.
The penetration depth for a good conductor can be calculated from the following equation: [5] =, where δ is the penetration depth (m), f is the frequency (Hz), μ is the magnetic permeability of the material (H/m), and σ is the electrical conductivity of the material (S/m).
A better choice for vacuum systems is the tin-silver eutectic, Sn95Ag5 (Sn-Ag eutectic is actually 96.5-3.5); its melting point of 230 °C (446 °F) allows bakeout up to 200 °C (392 °F). A similar 95-5 alloy, Sn95Sb5, is unsuitable as antimony has similar vapor pressure as lead.
Get AOL Mail for FREE! Manage your email like never before with travel, photo & document views. Personalize your inbox with themes & tabs. You've Got Mail!
The total energy in the space occupied by the system includes a component arising from the energy of a magnetic field in a vacuum. This component equals U v a c u u m = B e 2 V 2 μ 0 {\displaystyle U_{vacuum}={\frac {B_{e}^{2}V}{2\mu _{0}}}} , where μ 0 {\displaystyle \mu _{0}} is the permeability of free space , and isn't included as a part ...