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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").
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.
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 ...
Moghadasi et alios [10] evaluated Corey, Chierici and LET correlations for oil/water relative permeability using a sophisticated method that takes into account the number of uncertain model parameters. They found that LET, with the largest number (three) of uncertain parameters, was clearly the best one for both oil and water relative permeability.
Ramsay grease is an old composition of paraffin wax, vaseline and natural rubber, usable up to about 25 °C, for low vacuums to about 1 Pa. Krytox is a fluorether-based vacuum grease, useful from −75 to over 350 °C, not flammable even in liquid oxygen, and highly resistant to ionizing radiation. Polyphenyl ether greases
Transformer oil or insulating oil is an oil that is stable at high temperatures and has excellent electrical insulating properties. It is used in oil-filled wet transformers, [ 1 ] some types of high-voltage capacitors , fluorescent lamp ballasts , and some types of high-voltage switches and circuit breakers.
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High-power RF power tubes are directly heated; the heater voltage must be much smaller than the signal voltage on the grid and is therefore in the 5...25 V range, drawing up to hundreds of amperes from a suitable heater transformer. In some valve part number series, the voltage class of the heater is given in the part number, and a similar ...