(physics) The difference between the phase of a sinusoidally varying quantity and the phase of a second quantity which varies sinusoidally at the same frequency. Also known as phase difference.
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A conducting bar that carries heavy currents to supply several electric circuits , Usually made of brase, zero resistance. High Current Carrying Capacity
busbar
1500 ampere busbars within a power distribution rack for a large buildingA busbar refers in electrical power distribution to thick strips of copper or other material that conduct electricity around a switchboard, distribution board, substation, or other electrical apparatus.
The size of the busbar determines the maximum amount of current that can be safely carried. Small distribution boards or consumer units may have busbars which have a cross sectional area of as little as 10 mm2 but large electrical substations may use metal tubes of 50 mm or more in diameter as busbars.
Busbars are typically either flat strips or hollow tubes as these shapes allow heat to dissipate more efficiently due to their high surface area to cross-sectional area ratio. The skin effect makes AC busbars more than about 8 mm (1/3 in) thick inefficient.
Busbars are usually suitably insulated for the voltage which they carry. The busbar may either be supported on insulators, or else insulation may completely surround the busbar. Busbars are protected from accidental contact either by being surrounded in a sheet metal enclosure or by being placed out of normal reach. Neutral busbars may also be insulated. Earth busbars are typically bolted directly onto any metal chassis of their enclosure.
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Blocking of customer access to energy, usually due to temporary shortage of supply. Load shedding is rare, and is most commonly applied during times of emergency or severe shortage. In most cases, the first loads a utility will shed in these conditions are loads required by industrial and commercial customers. Institutional loads are typically the last to be shed since public institutions (hospitals, schools, municipal lighting authorities, etc.) are considered to be a utility's most essential customers.
Switchgrass, a hardy plant used in the biofuel industry in the United StatesIn energy production and industry, biomass refers to living and recently living biological material which can be used as fuel or for industrial production. Most commonly biomass refers to plant matter grown for use as biofuel, but also includes plant or animal matter used for production of fibres, chemicals or heat. It excludes organic material which has been transformed by geological processes into substances such as coal or petroleum. It is usually measured by dry weight.
The term biomass is especially useful for plants, where some internal structures may not always be considered living tissue, such as the wood (secondary xylem) of a tree.
Biofuels include bioethanol, biobutanol and biodiesel; these two last ones are direct biofuels (so they can be used directly in petroleum engines).
Biomass is grown from several plants, including switchgrass, hemp, corn, and sugarcane. The particular plant used is usually not important to the end product. Production of biomass is a growing industry as interest in sustainable fuel sources is growing.
Biomass may also include animal waste, which may be burnt as fuel.
Other uses of biomass, besides fuel:
building materials
biodegradable plastics and paper (using cellulose fibers)
Though biomass is a renewable fuel, it can still contribute to Global Warming. This happens when the natural carbon equilibrium is disturbed; for example by deforestation or urbanization of green sites.
Biomass is part of the carbon cycle. Carbon from the atmosphere is converted into biological matter by photosynthesis. On decay or combustion the carbon goes back into the atmosphere. This happens over a relatively short timescale and plant matter used as a fuel can be constantly replaced by planting for new growth. Therefoe a reasonably stable level of atmospheric carbon results from its use as a fuel.
Although fossil fuels have their origin in ancient biomass, they are not considered biomass by the generally accepted definition because they contain carbon that has been 'out' of the carbon cycle for a very long time. Their combustion therefore disturbs the carbon dioxide content in the atmosphere.
- The circular mil is a unit of area used especially when denoting the cross-sectional size of a wire or cable. It is the equivalent area of a circle whose diameter is 0.001 (10-3) inch, or approximately 0.7854 millionths of a square inch (or 2.5 x 10-7 times pi).
In plane geometry, area always varies in direct proportion to the square of the linear dimension. Thus, if wire A is twice the diameter of wire B, then wire A has four times the cross-sectional area, in circular mils, of B. If wire C is 1/5 of the diameter of wire D, then C has 1/25 the cross-sectional area, in circular mils, of D. In this respect, the circular mil is like any other unit for measurement of area.
Because the circular mil is, as its name implies, based on a circular unit of measure rather than a rectangular unit, conversions between circular mils and square units such as the meter squared (m2) or centimeter squared (cm2) can be awkward. To convert circular mils approximately to meters squared (m2), multiply by 5.066 x 10-10. Conversely, multiply by 1.974 x 109. To convert circular mils approximately to centimeters squared (cm2), multiply by 5.066 x 10-6. Conversely, multiply by 1.974 x 105.
Also see area, meter squared, centimeter squared, foot squared, International System of Units (SI), and Table of Physical Units.